Position command generating device

ABSTRACT

A command generating device includes a command shape calculating unit for calculating an nth derivative command shape which is a fixed multiple of the nth derivative with respect to time of a position command for causing a machine to reach a target position at a positioning time so that a convolution of a velocity command which is the first derivative with respect to time of the position command and the impulse response of a transfer function determined from the frequency of a vibration which occurs in the machine becomes equal to zero, the convolution being calculated over the time period from the positioning time onward, and an associating processing unit for integrating the nth derivative command shape n times with respect to time, and for multiplying the integral result by a constant which associates the position command at the positioning time with the target position so as to determine the position command.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 11/249,351, filed Oct. 14, 2005, which is incorporated herein byreference, and claims the benefit of Japanese Patent Application No.2005-112344, filed Apr. 8, 2005.

FIELD OF THE INVENTION

The present invention relates to a command generating device thatprovides a command to a control device for driving and controlling anactuator for actuating a machine, particularly a machine with lowrigidity.

BACKGROUND OF THE INVENTION

There have been provided related art command generating devices whichcan suppress vibrations at the time of actuation of a machine byinserting a filter, such as a notch filter, into a path via which acommand for positioning and actuating the machine is delivered to themachine, so as to eliminate signal components having frequencies equalto the resonance frequencies of vibrations which can occur in themachine from the command (refer to, for example, patent reference 1).

An apparatus disclosed by patent reference 2 forms a command based on aphase plane which is based on a dynamic behavior of a target machine tobe driven when changing an acceleration command stepwise according tothe period of a vibration which occurs in the machine. The apparatusdisclosed by patent reference 2 thus suppresses deformation in themachine to static deformation or less to enable the machine to move at ahigh velocity.

As disclosed by patent reference 3, there has been provided a commandgenerating method of defining a vibration model for a target machine tobe driven, and determining coefficient parameters about a polynomialshape command by performing calculations, such as calculations ofsimultaneous linear equations with more than one unknown, underconditions that the machine stops at a positioning start time and apositioning time, based on this model, thereby making the machine, suchas a flexible structure with low rigidity, follow the command.

A method disclosed by patent reference 4 can suppress vibrations whichoccur in a target machine to be driven when the machine moves byproviding a command having an acceleration time period and adeceleration time period which are integral multiples of the mechanicalvibration period, respectively.

[Patent reference 1] JP, 2003-65385,A[Patent reference 2] Japanese patent No. 2551868[Patent reference 3] JP, 2002-91570,A[Patent reference 4] JP, 54-98477,A

DISCLOSURE OF THE INVENTION

A problem with the related art command generating device disclosed bypatent reference 1 is that the filter which is inserted into the pathfor delivery of the positioning command increases the command outgoingtime as compared with the command outgoing time which is provided to thecommand before the insertion of the filter, and this results in a delayin the positioning operation with respect to a desired positioning time.Another problem is that when a notch filter is used as the filter, sincethe command signal is shaped so as to have a shape which changessteeply, vibrations of higher mode can be easily excited, and thereforethe related art command generating device cannot cause the actuator tooperate according to the command which has such a steep change becausethe equipment to be driven does not have sufficiently-high trackingcharacteristics.

A problem with the apparatus disclosed by patent reference 2 is thatsince the acceleration command shape changes stepwise, the commandsignal contains many high-frequency components and hence easily excitevibrations of higher mode, and therefore the related art apparatuscannot cause the actuator to operate according to the command as long asthe equipment to be driven does not have sufficiently-high trackingcharacteristics.

A problem with the method disclosed by patent reference 3 is that it isimpossible to predict what kind of shape the calculated shape commandhas before the calculation of the coefficient parameters, and thereforeit cannot be denied that there is a possibility that the calculatedshape command has a shape unsuitable for the positioning command signal,such as a shape which causes the target machine to pass the targetposition once, and to move backward and reach the target position.

Another problem is that when the number of conditions for thecoefficient matrix of the simultaneous linear equations with more thanone unknown is large on calculating solutions of the simultaneous linearequations, the formation of the command value with the coefficientsincluding the error causes residual vibrations because it cannot satisfyend conditions strictly, and the target machine may be positioned to aposition different from the target position at the worst.

A problem with the method disclosed by patent reference 4 is that it isimpossible to determine the acceleration and deceleration time periodsarbitrarily, and therefore, especially in a case where a velocitycommand shape is a triangular one, the application of the related artmethod makes it impossible to position the target machine at a desiredpositioning time.

The present invention is made in order to solve the above-mentionedproblems, and it is therefore an object of the present invention toprovide a command generating device that provides a command which canposition even a machine with low rigidity at a desired positioning timewithout exciting any vibration in the machine.

In accordance with the present invention, there is provided a commandgenerating device including: a command shape calculating unit forcalculating an nth derivative command shape signal having a value whichis equal to a fixed multiple of an nth derivative with respect to timeof a position command for causing a target to be driven and controlledto reach a target position at a positioning time so that a convolutionof a velocity command which is a first derivative with respect to timeof the position command and an impulse response of a transfer functionwhich is determined from a frequency of a vibration which occurs in thetarget to be driven and controlled becomes equal to zero, theconvolution being calculated over the time period from the positioningtime onward; and an associating processing unit for integrating the nthderivative command shape signal which is calculated from the positioncommand by the command shape calculating unit n times with respect totime, and for multiplying the integral result by a constant whichassociates the position command at the positioning time with the targetposition so as to determine the position command.

As previously mentioned, the command generating device includes thecommand shape calculating unit for calculating the nth derivativecommand shape signal having a value which is equal to a fixed multipleof the nth derivative with respect to time of a position command forcausing the target to be driven and controlled to reach the targetposition at the positioning time so that the convolution of the velocitycommand which is the first derivative with respect to time of theposition command and the impulse response of the transfer function whichis determined from the frequency of the vibration which occurs in thetarget to be driven and controlled becomes equal to zero, theconvolution being calculated over the time period from the positioningtime onward, and the associating processing unit for integrating the nthderivative command shape signal which is calculated from the positioncommand by the command shape calculating unit n times with respect totime, and for multiplying the integral result by the constant whichassociates the position command at the positioning time with the targetposition so as to determine the position command. Therefore, the presentinvention offers an advantage of being able to provide a command whichmaking it possible to perform a positioning operation without any delayto the desired positioning time and without exciting any vibration inthe target to be driven and controlled even if the target is a machinewith low rigidity.

Further objects and advantages of the present invention will be apparentfrom the following description of the preferred embodiments of theinvention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram showing the structure of an actuating controlsystem for actuating a machine, to which a command generating device inaccordance with embodiment 1 of the present invention is applied;

FIG. 2 is a flowchart showing an operation of generating a positioncommand X*(t) in accordance with embodiment 1;

FIG. 3 is a diagram showing an example of an acceleration command shapein accordance with embodiment 1;

FIGS. 4A to 4C are diagrams showing command shapes in accordance withembodiment 1;

FIGS. 5A to 5C are diagrams showing command shapes in accordance withembodiment 1;

FIGS. 6A and 6B are diagrams showing the shape of an S-curveacceleration-and-deceleration command;

FIG. 7 is a block diagram showing the structure of an actuating controlsystem for actuating a machine, to which a command generating device inaccordance with embodiment 2 of the present invention is applied;

FIG. 8 is a flowchart showing an operation of generating a positioncommand X*(t) in accordance with embodiment 2;

FIGS. 9A and 9B are diagrams showing the shape of an accelerationcommand and that of a velocity command which is obtained by integratingthe acceleration command once with respect to time;

FIG. 10 is a block diagram showing the structure of a command generatingdevice in accordance with embodiment 3 of the present invention;

FIG. 11 is a flowchart showing an operation of generating a positioncommand X*(t) in accordance with embodiment 3;

FIG. 12 is a diagram showing table 1 which is used when calculatingcommand shapes;

FIGS. 13A and 13B are diagrams showing the shape of an S-curveacceleration-and-deceleration command in accordance with embodiment 1;

FIGS. 14A and 14B are graphs showing a numerical calculation example towhich a triangle-shaped velocity command is applied;

FIGS. 15A and 15B are a numerical calculation example in which a commandshape is given by equation (26) and a ratio parameter r=0.4, the examplebeing not pursuant to embodiment 3;

FIGS. 16A and 16B are graphs showing a numerical calculation example ofcommand shapes in accordance with embodiment 3;

FIG. 17 is a diagram showing an acceleration command shape A**(t) inaccordance with embodiment 3;

FIG. 18 is a diagram showing an acceleration command shape in accordancewith embodiment 4;

FIG. 19 is a diagram showing table 2 which used when calculating theacceleration command shape in accordance with embodiment 4;

FIG. 20 is a diagram showing the acceleration command shape inaccordance with embodiment 4;

FIG. 21 is a flowchart showing a process of calculating a positioncommand which is carried out by a command generating device inaccordance with embodiment 6;

FIGS. 22A to 22C are graphs showing a numerical calculation example towhich the position command in accordance with embodiment 6 is notapplied, but to which a position command which offers a triangle-shapedvelocity command is applied;

FIGS. 23A to 23C are graphs showing a numerical calculation example towhich the position command in accordance with embodiment 6 is applied;

FIG. 24 is a block diagram showing the structure of an actuating controlsystem for actuating a machine, to which a command generating device inaccordance with embodiment 7 of the present invention is applied;

FIG. 25 is a flowchart showing an operation of generating a commandwhich is performed by the command generating device in accordance withembodiment 7;

FIGS. 26A and 26B are graphs showing a velocity command and anacceleration command in accordance with embodiment 7;

FIGS. 27A and 27B are graphs showing a velocity command and anacceleration command in accordance with embodiment 7;

FIG. 28 is a block diagram showing another example of the structure ofthe actuating control system for actuating a machine, to which thecommand generating device in accordance with embodiment 7 of the presentinvention is applied;

FIG. 29 is a block diagram showing the structure of an actuating controlsystem for actuating a machine, to which a command generating device inaccordance with embodiment 8 of the present invention is applied;

FIG. 30 is a flowchart showing an operation of generating a commandwhich is performed by the command generating device in accordance withembodiment 8;

FIG. 31 is a block diagram showing the structure of an actuating controlsystem for actuating a machine, to which a command generating device inaccordance with embodiment 9 of the present invention is applied;

FIG. 32 is a flowchart showing an operation of generating a positioncommand which is performed by the command generating device inaccordance with embodiment 9;

FIG. 33 is a flowchart explaining a command generation processing A;

FIG. 34 is a flowchart explaining a command generation processing B;

FIG. 35 is a flowchart explaining a command generation processing C;

FIG. 36 is a flowchart explaining a command generation processing D;

FIG. 37 is a flowchart explaining a command generation processing E;

FIGS. 38A to 38D are graphs showing a numerical calculation example towhich the position command in accordance with embodiment 9 is notapplied, but to which a trapezoid-shaped velocity command is applied;and

FIGS. 39A to 39D are graphs showing a numerical calculation example towhich the position command in accordance with embodiment 9 is applied.

PREFERRED EMBODIMENTS OF THE INVENTION Embodiment 1

FIG. 1 is a block diagram showing the structure of a drive controlsystem for actuating and controlling a machine, to which a commandgenerating device in accordance with embodiment 1 of the presentinvention is applied. In the figure, the actuating control system isprovided with the command generating device 1 in accordance with thisembodiment, an actuator drive controller 2, an actuator 3, and themachine (i.e., a target to be driven and controlled) 4 which is drivenand controlled by the actuator.

The actuator drive controller 2 supplies drive energy to the actuator 3so as to control actuation of the machine 4 using the actuator 3. Forexample, when the actuator 3 is a servo motor, the actuator drivecontroller 2 is a servo amplifier which supplies a current to the servomotor. The actuator drive controller 2 can perform feedback control byusing a control loop in which it compares a target command with adetected value, or can control the actuator by using an open loop whichis not a control loop. As an alternative, the actuator drive controller2 can perform two-degree-of-freedom control or the like.

The actuator 3 provides an actuating force directly to the machine 4 soas to drive the machine. The actuator 3 has only to drive the machine 4.For example, the actuator 3 can be a rotation servo motor, a linearmotor, a stepping motor, a hydraulic motor, a piezo-electric element, orthe like. The machine 4 is made to perform a desired positioningoperation according to the actuating force generated by the actuator 3.Although the machine 4 can be a robot, a driving unit used forsemiconductor manufacturing apparatus, or the like, for example, themachine 4 can be anything which requires point to point control. Ingeneral, since the machine 4 has parts with low rigidity, thepositioning operation performed by the machine causes a vibration whichoriginates from the parts with low rigidity at the time when the machinestops and this results in making the settling characteristics at thetime of positioning worse.

The command generating device 1 provides a position command X*(t) to theactuator drive controller 2 at each time t based on a distance D(referred to as a target position D from here on) between a currentposition and a desired position to which the machine is to bepositioned, a positioning time 2 t ₀, the vibration frequency ω of themachine, and the vibration damping coefficient ζof the machine. Thecommand generating device 1 has a command shape calculating unit 5 andan associating processing unit 6. The position command X*(t) starts atthe time t=0, and becomes X*(2 t ₀)=D at the time t=the positioning time2 t ₀.

When the command generating device 1 generates the position commandX*(t), the command shape calculating unit 5 calculates an nth derivativecommand shape signal having a value which is equal to a fixed multipleof the nth derivative with respect to time of the position command X*(t)so that a convolution of the impulse response of a transfer functionwhich is determined from both the vibration frequency ω and vibrationdamping coefficient ζ of the machine 4, and a velocity command V*(t)which is the first derivative with respect to time of the positioncommand X*(t) becomes equal to zero, the convolution being calculatedover the time period from the positioning time onward. The associatingprocessing unit 6 integrates the nth derivative command shape signalwhich is calculated from the position command X*(t) n times with respectto time and multiplies the integral result by a constant so as toassociate the position command at the positioning time with the targetposition D.

Next, the operation of the command generating device in accordance withthis embodiment of the present invention will be explained. FIG. 2 is aflowchart showing an operation of generating the position command X*(t)of the command generating device in accordance with embodiment 1. Thedetails of the generating operation will be explained with reference tothis flow and FIG. 1. First, a desired positioning time 2 t ₀ and atarget position D for the positioning operation of the machine 4 areinputted into the command generating device 1 (in step ST1). Next, instep ST2, the vibration frequency ω of the machine 4 which is acquiredbeforehand for the machine 4 is inputted into the command generatingdevice 1. For example, when the machine performs the positioningoperation in advance, a vibration which occurs in the machine 4 ismonitored and the frequency of the vibration is determined.

Next, the command shape calculating unit 5 in the command generatingdevice 1 calculates a command shape (i.e., an nth derivative commandshape signal) from the position command X*(t) in steps ST3 to ST4.First, in step ST3, the command shape calculating unit 5 determines anacceleration command shape A**(t) from the second derivative withrespect to time of the position command X*(t). The acceleration commandshape A**(t) is equal to a fixed multiple of an acceleration commandA*(t) which is the second derivative with respect to time of theposition command X*(t). That is, a certain constant k exists and thefollowing relationship: A**(t)=kA*(t) is established between A**(t) andA*(t).

FIG. 3 is a diagram showing an example of the acceleration command shapeA**(t) which is generated by the command generating device in accordancewith embodiment 1. In the figure, the acceleration command shape A**(t)is defined by the following equations (1) and (2). Next, a case wherethe command shape calculating unit 5 selects a shape as shown in FIG. 3from among shapes which are pre-registered as the acceleration commandshape A**(t) for the positioning operation of the machine 4 will beexplained as an example. Time periods tA, tB, tC, and tD have a timelength rxt₀. The time periods tA and tC are rising ones which specifythe trapezoidal shape of the acceleration command shape A**(t), and thetime periods tB and tD are falling ones which specify the trapezoidalshape of the acceleration command shape A**(t).

$\begin{matrix}{{A^{**}(t)} = {{a^{**}(t)} - {a^{**}\left( {{2t_{0}} - t} \right)}}} & (1) \\{{a^{**}(t)} = \left\{ \begin{matrix}{ct} & \left( {0 \leqq t \leqq {rt}_{0}} \right) \\{crt}_{0} & \left( {{rt}_{0} < t < {\left( {1 - r} \right)t_{0}}} \right) \\{{- {ct}} + {ct}_{0}} & \left( {{\left( {1 - r} \right)t_{0}} \leqq t \leqq t_{0}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (2)\end{matrix}$

where c is a constant (it can be safely said that c=1), and r is aparameter and is defined as (the time required for the accelerationcommand shape to reach the highest acceleration from 0)/t₀.

Next, the command shape calculating unit 5 calculates the parameter rusing the inputted vibration frequency ω of the machine 4 according tothe following equation (3) (in step ST4)

r=1−[t ₀ω)/(2π)](2π/ω/t ₀)  (3)

The command shape calculating unit 5 then defines the time required forthe acceleration command shape signal to have the highest accelerationvalue from 0 using the following equation (4), and determines theacceleration command shape signal.

t₀−[t₀ω/(2π)](2π/ω)  (4)

The notation [z] in the above-mentioned equation is Gauss' notationshowing the largest integer value that does not exceed z.

When the command shape calculating unit 5 determines the accelerationcommand shape signal as mentioned above, the associating processing unit6 carries out a process of associating the position command at thepositioning time with the target position D based on the accelerationcommand shape signal (in step ST5). To be more specific, the associatingprocessing unit 6 integrates the acceleration command shape A**(t) whichis obtained in the above-mentioned step twice according to the followingequation (5), and obtains the position command X*(t) by multiplying theintegral result by the constant C which causes the machine to move tothe target position D at the positioning time 2 t ₀.

$\begin{matrix}{{{X^{*}(t)} = {C \times {\int_{0}^{t}{\int_{0}^{\tau 1}{{A^{**}(\tau)}\ {\tau}\ {\tau_{1}}}}}}}{C = \frac{D}{\int_{0}^{2t\; 0}{\int_{0}^{\tau \; 1}{{A^{**}(\tau)}\ {\tau}\ {\tau_{1}}}}}}} & (5)\end{matrix}$

As will be explained below, when the machine 4 performs the positioningoperation, the machine 4 can be made to operate in response to theposition command X*(t) generated according to the above-mentionedprocedure without any vibration being excited at the time when themachine is stopped.

First, an expression (6) of the machine's final position X(t) with theposition command X*(t), which is determined by the vibration frequency ωof the machine, is given as follows:

$\begin{matrix}{{\hat{X}(s)} = {\frac{\omega^{2}}{s^{2} + \omega^{2}}{{\hat{X}}^{*}(s)}}} & (6)\end{matrix}$

where s is the Laplacian operator, and X(s) hat and X*(s) hat (hatphonetically means ̂) are Laplace transforms of X(t) and X*(t),respectively.

When a velocity command V*(t) which is the first derivative with respectto time of the position command X*(t), and the machine's final velocityV(t) are used, the following equation (7) is established similarly.

$\begin{matrix}{{\hat{V}(s)} = {\frac{\omega^{2}}{s^{2} + \omega^{2}}{{\hat{V}}^{*}(s)}}} & (7)\end{matrix}$

where V*(s) hat is a Laplace transform of V*(t), and V(s) hat is aLaplace transform of the machine's final velocity V(t) (also in thiscase, hat phonetically means ̂).

When the above-mentioned equation (7) is rewritten in the form of timedomain using sin ωt which is the impulse response of a transfer functionω²/(s²+ω²), the following equation (8) is obtained. For the positioningtime 2 t ₀, the velocity command V*(t) has a shape which is symmetricwith respect to the time to as shown in the following equation (9). Inthis case, v*(t) has a relationship shown by the following equation(10).

$\begin{matrix}{{V(t)} = {\int_{0}^{t}{\sin \; {\omega \left( {t - \tau} \right)}{V^{*}(\tau)}\ {\tau}}}} & (8) \\{{V^{*}(t)} = {{v^{*}(t)} + {v^{*}\left( {{2\; t_{0}} - t} \right)}}} & (9) \\{{v^{*}(t)}\left\{ \begin{matrix}{\neq {0\mspace{14mu} \left( {0 < t \leqq t_{0}} \right)}} \\{= ({otherwise})}\end{matrix} \right.} & (10)\end{matrix}$

At this time, the acceleration command A*(t) which is the secondderivative with respect to time of the position command X*(t), and ajerk command J*(t) which is the third derivative with respect to time ofthe position command X*(t) are given by the following equations,respectively:

A*(t)=a*(t)—a*(2t ₀ −t), a*(t)=dv*(t)/dt

J*(t)=j*(t)+j*(2t ₀ −t), j*(t)=da*(t)/dt

where a*(t)=0 and j*(t)=0 at times t<=0 and t>t₀, as can be seen fromthe above-mentioned equation (10).

FIGS. 4A to 4C are diagrams showing the shapes of the velocity command,acceleration command, and jerk command which are generated by thecommand generating device in accordance with embodiment 1. FIG. 4A showsthe velocity command V*(t), FIG. 4B shows the acceleration commandA*(t), and FIG. 4C shows the jerk command J*(t). Furthermore, FIGS. 4Ato 4C show that when V(t)=0 is established at any time after thepositioning time 2 t ₀, i.e., t>=2 t ₀, in the above-mentioned equation(8), the machine 4 continues to stop without any vibration being excitedtherein. Substitution of the above-mentioned equation (9) into theabove-mentioned equation (8) and use of the fact that V*(t)=0 at t>=2 t₀ and v*(t)=0 at t>t₀ and at t<=0 yields the following equation (11)about V(t). Transformation of variables of integration and sinω(t₀−τ)+sin ω(t−2 t ₀+τ)=2 sin ω(t−t₀)cos(t₀−τ) which is a formula ofthe trigonometric functions are used for the deformation of theabove-mentioned equation (8) to the following equation (11).

$\begin{matrix}\begin{matrix}{{V(t)} = {\int_{0}^{2\; t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}\left\{ {{v^{*}(\tau)} + {v^{*}\left( {{2\; t_{0}} - \tau} \right)}} \right\} \ {\tau}}}} \\{= {{\int_{0}^{t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}{v^{*}(\tau)}\ {\tau}}} + {\int_{t\; 0}^{2t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}{v^{*}\left( {{2\; t_{0}} - \tau} \right)}\ {\tau}}}}} \\{= {{\int_{0}^{t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}{v^{*}(\tau)}\ {\tau}}} + {\int_{0}^{t\; 0}{\sin \; {\omega \left( {t - {2t_{0}} + \tau} \right)}{v^{*}(\tau)}\ {\tau}}}}} \\{= {2\; \sin \; {\omega \left( {t - t_{0}} \right)}{\int_{0}^{t\; 0}{\cos \; {\omega \left( {t_{0} - \tau} \right)}{v^{*}(\tau)}\ {\tau}}}}}\end{matrix} & (11)\end{matrix}$

The integral part of the above-mentioned equation (11) is shown by thefollowing equation (12) by using the formula of integration by parts andthe fact that v*(0)=0 at t>t₀ and at t<=0 in the above-mentionedequation (10). Therefore, in order to make V(t) be equal to 0 at t>=2 t₀ in the above-mentioned equation (8), what is necessary is just to lookfor v*(t), a*(t), or j*(t) which satisfies either of three conditionsexpressed by the following equations (13), (14), and (15). As a result,commands which prevent occurrence of vibrations can be generated.

$\begin{matrix}\begin{matrix}{{\int_{0}^{t\; 0}{\cos \; {\omega \left( {t_{0} - \tau} \right)}v*(\tau)\ {t}}} = {\left\lbrack {{- \frac{1}{\omega}}\sin \mspace{11mu} {\omega \left( {t_{0} - \tau} \right)}v*(\tau)} \right\rbrack_{0}^{t_{0}} -}} \\{{\int_{0}^{t\; 0}{\left\{ {{- \frac{1}{\omega}}\ \sin \mspace{11mu} {\omega \left( {t_{0} - \tau} \right)}} \right\} a*(\tau){t}}}} \\{= {\frac{1}{\omega}{\int_{0}^{t\; 0}{\sin \mspace{11mu} {\omega \left( {t_{0} - \tau} \right)}a*(\tau \ ){t}}}}} \\{= {{\frac{1}{\omega^{2}}\left( {{a*\left( t_{0} \right)} - {\cos \mspace{11mu} \omega \; t_{0}a*(0)}} \right)} -}} \\{{\frac{1}{\omega^{2}}{\int_{0}^{t\; 0}{\cos \mspace{11mu} {\omega \left( {t_{0} - \tau} \right)}j*(\tau)\ {t}}}}}\end{matrix} & (12) \\{{\int_{0}^{t\; 0}{\cos \mspace{11mu} {\omega \left( {t - \tau} \right)}v*(\tau)\ {\tau}}} = 0} & (13) \\{{\int_{0}^{t\; 0}{\sin \mspace{11mu} {\omega \left( {t_{0} - \tau} \right)}a*(\tau)\ {\tau}}} = 0} & (14) \\{{{\int_{0}^{t\; 0}{\cos \mspace{11mu} {\omega \left( {t_{0} - \tau} \right)}j*(\tau)\ {\tau}}} = 0}{{{a*\left( t_{0} \right)} - {\cos \mspace{11mu} \omega \; t_{0}a*(0)}} = 0}} & (15)\end{matrix}$

The above-mentioned equations (13), (14), and (15) express not only theconditions on which the machine 4 stops without any vibration beingexcited at only the positioning time 2 t ₀, but stronger conditions onwhich the machine continues to stop without any vibration being excitedevent after the positioning time, i.e., at t>=2 t ₀. The formation ofthe velocity, acceleration, or jerk command which satisfies either oneof the conditional expressions can raise the effect of prevention ofvibrations.

It is clear from the above-mentioned equations (13), (14), and (15) thatthe same relationship is established among the velocity command shapeV**(t), acceleration command shape A**(t), and jerk command shape J**(t)which are equal to fixed multiples of V*(t), A*(t), and J*(t),respectively.

That is, when v**(t) is defined as kv*(t), a**(t) is defined as ka*(t),and j**(t) is defined as kj*(t), where k is a certain constant, and thevelocity command shape V**(t) is defined as v**(t)+v**(2 t₀−t), theacceleration command shape A**(t) is defined as a**(t)—a**(2 t ₀−t), andthe jerk command shape J**(t) is defined as j**(t)+j**(2 t ₀−t), thefollowing equations (16), (17), and (18) are established.

∫₀ ^(t0) cos ω(t−τ)ν**(τ)dτ=0  (16)

∫₀ ⁰ sin ω(t ₀−τ)a**(τ)dτ=0  (17)

∫₀ ⁰ cos ω(t ₀−τ)j**(τ)dτ=0a**(t ₀)−cos ωt ₀ a**(0)=0  (18)

The command generating device 1 can form commands which do not exciteany vibration when the machine performs the positioning operation byusing a command shape which satisfies either one of the above-mentionedequations (16), (17), and (18) Then, the command shape calculating unit5 looks for a command shape which satisfies either one of theabove-mentioned equations (16), (17), and (18) from among the velocitycommand shape V**(t), acceleration command shape A**(t), and jerkcommand shape J**(t). That is, the command shape calculating unit 5calculates an nth derivative command shape signal (n=1, 2, or 3 in theabove-mentioned case) from the position command X*(t) so that aconvolution of the impulse response of a transfer function which isdetermined from the vibration frequency ω of the machine as given by theabove-mentioned equation (8) and the velocity command becomes equal tozero, the convolution being calculated over the time period from thepositioning time onward.

After that, the command shape calculating unit 5 calculates a positioncommand shape X**(t) by integrating the nth derivative command shapesignal which is obtained from the position command X*(t) n times withrespect to time. Although the position command shape X**(t) thusobtained can suppress vibrations, X**(2 t ₀) is not equal to D at thepositioning time 2 t ₀. Therefore, the associating processing unit 6multiplies X**(t) by a constant which associates the position command atthe positioning time with the target position D so as to obtain theposition command X*(t). This processing corresponds to theabove-mentioned equation (5). When t=2 t ₀ is substituted into theabove-mentioned equation (5), X(2 t ₀) becomes equal to D.

A jerk command shape J**(t)=j**(t)+j**(2 t ₀−t) in which j**(t) is givenby the following equation (19) can be obtained as an example whichsatisfies the above-mentioned equations (18).

$\begin{matrix}{{j**(t)} = \left\{ \begin{matrix}c & \left( {{0\underset{\underset{\_}{\_}}{< t}\mspace{11mu} {\underset{\underset{\_}{\_}}{< t}}_{0}} - {2\; {\pi/\omega}}} \right) \\0 & \left( {{t_{0} - {2\; {\pi/\omega}}} < t < {2\; {\pi/\omega}}} \right) \\{{- c}\;} & \left( {2\; {\pi/\omega}\underset{\underset{\_}{\_}}{< t}\mspace{11mu} {\underset{\underset{\_}{\_}}{< t}}_{0}} \right)\end{matrix} \right.} & (19)\end{matrix}$

where c is an arbitrary positive constant in the above-mentionedequation (19), and it can be safely said that c=1.

FIGS. 5A to 5C are diagrams showing command shapes generated by thecommand generating device in accordance with embodiment 1. FIG. 5A showsa jerk command shape j**(t) during a time period [0, t₀], FIG. 5B showsan acceleration command shape a**(t) during the time period [0, t₀], andFIG. 5C shows a velocity command shape v**(t) during the time period [0,t₀]. As shown in FIG. 5A, the jerk command shape j**(t) has two pulseshaving constant values and having duration times tA and tB equal to rxtoduring a start and an end of the time period [0, t₀], respectively. rt₀is equal to the difference between to and the period of a vibration cosωt. As can be seen from FIG. 4A, the value of cos ω(t₀−t) during a timeperiod 0<=t<=tA becomes equal to that of cos ω(t₀−t) during a timeperiod t₀−tB<=t<=t₀. Therefore, the convolution of j**(t) and cos ωtduring the time period from the time t=0 to the time t=t₀ becomes equalto zero, that is, the first one of the above-mentioned equations (18) issatisfied.

By integrating this j**(t) once with respect to time, the accelerationcommand shape a**(t) during the time period [0, t₀] as shown in FIG. 5Bis obtained. The acceleration command shape having a trapezoidal shapetherefore becomes equal to zero at the times t=0 and to, i.e., a**(0)=0and a**(t₀)=0, and the following relationship: a**(t₀)−cos ωt₀a**(t)=0is satisfied. Therefore, it is understood that the second one of theabove-mentioned equations (18) is satisfied. The velocity command shapev**(t) during the time period [0, t₀] as shown in FIG. 5C is obtained byintegrating a**(t) once with respect to time.

In general, when to (>=2π/ω)) is provided, the jerk command shape j**(t)during the time period [0, t₀] is defined by a relationship given by thefollowing equation (20). The acceleration shape which is determined bythe above-mentioned equations (1), (2), and (3) is acquired byintegrating the jerk command shape J**(t)=j**(t)+j**(2 t ₀−t) once withrespect to time. This jerk command shape has two pulses having constantvalues and having a duration equal to the difference between t₀ and aproduct of the vibration period and [(t_(o)ω)/(2π)] during a start andan end of the time period [0, t₀], respectively. The jerk command shapemeets the first one of the above-mentioned equations (18), as well asthe above-mentioned equation (19).

$\begin{matrix}{{j**(t)} = \left\{ {{\begin{matrix}c & \left( {0 \leqq t \leqq {t_{0} - t_{A}}} \right) \\0 & \left( {{t_{0} - t_{A}} < t < t_{A}} \right) \\{{- c}\;} & \left( {t_{A} \leqq t \leqq t_{0}} \right)\end{matrix}{where}\mspace{14mu} t_{A}} = {\left( {2\; {\pi/\omega}} \right)\left\lbrack {\left( {t_{0} \times \omega} \right)/\left( {2\; \pi} \right)} \right\rbrack}} \right.} & (20)\end{matrix}$

A command pattern which makes the shape of the acceleration command be atrapezoidal one as mentioned above is currently called an S-curveacceleration-and-deceleration command pattern. FIGS. 6A and 6B arediagrams showing command shapes of an S-curveacceleration-and-deceleration command pattern which is generated asmentioned above. FIG. 6A shows an acceleration command A**(t), and FIG.6B shows a velocity command V**(t). In the S-curveacceleration-and-deceleration command pattern, since the accelerationcommand A**(t) has a continuous shape as shown in FIG. 6A, an advantageof softening shocks at the time of actuation of the machine is known.

The command generating device in accordance with this embodiment offersanother advantage of suppressing vibrations at the time of positioningcontrol in addition to this advantage. Conventionally, the parameter rin the above-mentioned equation (2) is determined by trial and error forthe S-curve acceleration-and-deceleration command pattern. In contrast,in accordance with this embodiment, the parameter r of the S-curveacceleration-and-deceleration command pattern can be determinedautomatically using the vibration frequency ω of the machine 4 and thepositioning operation time 2 t ₀.

When the command shapes in accordance with this embodiment 1 are used,V(t)=0 is established at the time t=2 t ₀ in the above-mentionedequation (8). As a result, the positioning operation can be completed atthe desired positioning time 2 t ₀. In other words, the positioningoperation can be performed without any delay to the desired positioningtime 2 t ₀. As shown in the flowchart of FIG. 2, complicated dataprocessing for obtaining the position command, such as solving higherorder equations, is not included in the positioning operation.Therefore, the command generating device 1 in accordance with thisembodiment 1 can be implemented without having to use any expensiveprocessor which can perform complicated data processing.

As shown in FIGS. 6A and 6B, the acceleration command during anacceleration time period (Q<=t<=t₀) or a deceleration time period(t₀<=t<=2 t ₀) is continuous, and does not experience any rapid changewhich rises during the acceleration time period (or during thedeceleration time period), after that, descends in a short time, andthen rises again. In this case, many high-frequency components are notcontained in the acceleration command signal. On the contrary, when theacceleration command signal is discontinuous or experiences a rapidchange which rises during the acceleration time period (or during thedeceleration time period), after that, descends in a short time, andthen rises again, it is clear that many high-frequency components arecontained in the acceleration command signal. When a command includingmany high-frequency components is provided to the actuator drivecontroller having a low degree of trackability (i.e., responsibility),the actuator drive controller and actuator cannot follow a steep motion,i.e., the high-frequency components of the command, and this results invibrations in the machine. In contrast, the command generating device inaccordance with the present invention can prevent vibrations resultingfrom the lack of the trackability of the actuator drive controller.

Two or more modes of vibration exist in the machine, and a dominant modeof vibration (usually, a low-frequency mode of vibration) affects themachine's operation in many cases. When the machine is made to operateaccording to a command including many high-frequency components, notonly a dominant mode of vibration but a higher-frequency mode ofvibration can be easily excited. The command generating device inaccordance with the present invention makes it difficult for such ahigher-frequency mode of vibration to be excited in the machine. Asmentioned above, the command generating device in accordance with thepresent embodiment offers an advantage of making it difficult forvibrations resulting from high-frequency components contained in thecommand to be excited in the machine.

As mentioned above, the command generating device in accordance withthis embodiment 1 is provided with the command shape calculating unit 5for calculating an nth derivative command shape signal having a value,which is equal to a fixed multiple of the nth derivative with respect totime of a position command for moving the machine 4 to a target positionD during the time period from the time t=0 to the time t=a positioningtime 2 t ₀, so that a convolution of a velocity command which is thefirst derivative with respect to time of the position command and theimpulse response of a transfer function which is determined from thefrequency ω of a vibration which occurs in the machine 4 when beingmoved becomes equal to zero, the convolution being calculated over thetime period from the positioning time onward, and the associatingprocessing unit 6 for integrating the nth derivative command shapesignal which is calculated from the position command by the commandshape calculating unit 5 n times with respect to time, and formultiplying the integral result by a constant which associates theposition command at the positioning time 2 t ₀ with the target positionD so as to determine the position command. Therefore, even if themachine 4 has low rigidity, the command generating device can provide acommand which can position the machine without any delay to the desiredpositioning time 2 t ₀ the machine without any vibration being excitedin the machine.

In order to obtain the position command X*(t) as shown by theabove-mentioned equation (5), the nth derivative command shape which isa fixed multiple of the nth derivative with respect to time of theposition command is calculated, the nth derivative command shape is thenintegrated n times with respect to time, and the integral result ismultiplied by the constant C which associates the position command atthe positioning time 2 t ₀ with the target position D. Therefore, theposition command X*(t) satisfies the condition that the position commandmust make the machine reach the target position at the positioning time,i.e., the condition that X*(2 t ₀)=D at the time t=2 t ₀, which is theone which the position command should satisfy at worst.

Embodiment 2

The position command explained in above-mentioned embodiment 1 is theone in which the positioning time is 2 t ₀, and the acceleration anddeceleration time periods are t₀, respectively. In contrast, a commandgenerating device in accordance with this embodiment 2 can generate aposition command in which a positioning time T₀, and acceleration anddeceleration time periods to are independently determined by usingcommand values explained in embodiment 1. A procedure of this embodimentwill be shown below.

FIG. 7 is a block diagram showing the structure of an actuating controlsystem for actuating and controlling a machine, to which the commandgenerating device in accordance with embodiment 2 of the presentinvention is applied. The command generating device in accordance withthis embodiment 2 differs from that of FIG. 1 in that the commandgenerating device in accordance with this embodiment 2 generates aposition command based on the positioning time T₀ and acceleration timeperiod (or deceleration time period) t₀.

Next, the operation of the command generating device in accordance withthis embodiment of the present invention will be explained. FIG. 8 is aflowchart showing an operation of generating the position command X*(t)which is performed by the command generating device in accordance withembodiment 2. This flowchart differs from that of FIG. 2 in that thepositioning time To and acceleration and deceleration time periods toare inputted independently to the command generating device in stepST101, and an acceleration command shape is defined asA**(t)=a**(t)+a**(T₀/2−t) in step ST103, where a**(t) is given by thefollowing equation (21):

$\begin{matrix}{{a**(t)} = \left\{ \begin{matrix}{ct} & \left( {0 \leqq t \leqq {rt}_{0}} \right) \\{crt} & \left( {t_{0} < t < {{t\left( {l - r} \right)}t_{0}}} \right) \\{{- {crt}} + {crt}_{0}} & \left( {{\left( {1 - r} \right)t_{0}} \leqq t \leqq t_{0}} \right) \\0 & \left( {t_{0} < t \leqq {T_{0}/2}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (21)\end{matrix}$

FIG. 9 shows the acceleration command shape A**(t) and a velocitycommand shape V**(t) which is an integral of the acceleration commandshape once with respect to time. It is apparent from comparison with thecase of generation of command values as shown in above-mentionedembodiment 1 that a time during of (T₀−2 t ₀) during which theacceleration is kept at zero is placed between the acceleration anddeceleration time periods of the acceleration command shape. After that,the command generating device calculates a parameter r from thevibration frequency ω and acceleration (or deceleration) time period toby using the above-mentioned equation (3), as shown in FIG. 2. Afterthat, the command generating device integrates the acceleration commandshape twice with respect to time, and obtains the position command X*(t)by multiplying the integral result by a constant which associates theposition command at the positioning time 2 t ₀ with a target position.

As will be explained below, when the machine 4 performs the positioningoperation, the machine 4 can be made to operate in response to theposition command X*(t) generated according to the above-mentionedprocedure without any vibration being excited at the time when themachine is stopped and without any delay to the desired positioningtime. In order that the positioning operation can be completed withoutany vibration being excited at the time when the machine is stopped andwithout any delay to the desired positioning time, the above-mentionedequation (18) has only to be established between the accelerationcommand shape and a jerk command shape. Since the positioning time isT₀, the above-mentioned equation (18) can be expressed by the followingequation (22):

$\begin{matrix}{{{\int_{0}^{\frac{T_{0}}{2}}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - \tau} \right)}{j**(\tau)}\ {t}}} = 0}{{{a**\left( {T_{0}/2} \right)} - {\cos \mspace{11mu} \omega \frac{T_{0}}{2}{a**(0)}}} = 0}} & (22)\end{matrix}$

Hereafter, it will be explained that the above-mentioned equation (21)meets the above-mentioned equations (22). The above-mentioned equations(22) show that the above-mentioned equation (21) meets the second one ofthe above-mentioned equations (22). Using the equation (21), j**(t) isgiven by the following equation (23). Using this equation, the left partof the first equation of the above-mentioned equations (22) can be givenby the following equation (24):

$\begin{matrix}{{j**(t)} = \left\{ \begin{matrix}c & \left( {0 \leqq t \leqq t_{0}} \right) \\0 & \left( {t_{0} < t < {\left( {1 - r} \right)t_{0}}} \right) \\{- c} & \left( {{\left( {1 - r} \right)t_{0}} \leqq t \leqq t_{0}} \right) \\0 & \left( {t_{0} < t \leqq {T_{0}/2}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (23) \\{{{\int_{0}^{\frac{T_{0}}{2}}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - \tau} \right)}{j**(\tau)}\ {t}}} = {{c{\int_{0}^{{rt}\; 0}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - \tau} \right)}{\tau}}}} - {c{\int_{{({l - r})}t\; 0}^{t\; 0}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - \tau} \right)}{\tau}}}}}}} & (24)\end{matrix}$

In the above-mentioned equation (3), if n=[t₀ω/(2π)] (the notation [x]is Gauss' notation showing the largest integer value that does notexceed x), n is an integer and (1-r)t₀=nx2π/ω). When a variabletransformation: t=τ−(1−r)t₀ is performed, the second term of theright-hand side of the above-mentioned equation (24) is expressed by thefollowing equation (25), and the right-hand side of the equation (24)becomes equal to zero. That is, it is understood that the first equationof the above-mentioned equations (22) is satisfied. Therefore, thepositioning control by using the position command X*(t) obtainedaccording to the flowchart of FIG. 8 can cause the machine to completethe positioning operation without any vibration being excited in themachine and without any delay to the desired positioning time.

$\begin{matrix}\begin{matrix}{{c{\int_{{({1 - r})}t\; 0}^{t\; 0}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - \tau} \right)}{\tau}}}} = {c{\int_{0}^{{rt}\; 0}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - t - {\left( {1 - r} \right)t_{0}}} \right)}{t}}}}} \\{= {c{\int_{0}^{{rt}\; 0}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - t - {n\frac{2\pi}{\omega}}} \right)}{t}}}}} \\{= {c{\int_{0}^{{rt}\; 0}{\cos \; \left\{ {{\omega \left( {\frac{T_{0}}{2} - t} \right)} - {2\; \pi \; n}} \right\} {t}}}}} \\{= {c{\int_{0}^{{rt}\; 0}{\cos \mspace{11mu} {\omega \left( {\frac{T_{0}}{2} - t} \right)}{t}}}}}\end{matrix} & (25)\end{matrix}$

As mentioned above, the command generating device in accordance withthis embodiment 2 offers an advantage of being able to set thepositioning time and acceleration and deceleration time periodsindependently, in addition to the advantages provided by that ofabove-mentioned embodiment 1.

Embodiment 3

FIG. 10 is a block diagram showing the structure of a command generatingdevice in accordance with embodiment 3 of the present invention. Thecommand generating device 1 in accordance with this embodiment 3 isprovided with a command shape calculating unit 5 and an associatingprocessing unit 6 which are explained in above-mentioned embodiment 1,and is also provided with a storage unit 7.

The command generating device 1 in accordance with this embodiment 3establishes an equation showing the frequency component of a commandshape signal including a parameter for specifying an nth derivativecommand shape which is equal to a fixed multiple of the nth derivativewith respect to time of a position command, the frequency componentvarying with a change in the parameter. The command generating device 1calculates frequencies at which the equation becomes equal to zerodependently upon the change in the parameter in advance. The storageunit 7 stores tabular data (also referred to as table 1 from here on)indicating a one-to-one correspondence between this parameter and boththe frequencies at which the frequency component of the command shapesignal becomes equal to zero and a positioning time.

In accordance with this embodiment 3, the command shape calculating unit5 selects a command shape, as will be shown below, in addition tocommand shapes given by the above-mentioned equation (1) and (2), withreference to the above-mentioned tabular data stored in the storage unit7.

Next, the operation of the command generating device in accordance withthis embodiment of the present invention will be explained. FIG. 11 is aflowchart showing an operation of generating a position command X*(t)which is performed by the command generating device in accordance withembodiment 3. The details of the generating operation will be explainedwith reference to this flow and FIG. 10. In this flowchart, step ST3 ofFIG. 2 shown in above-mentioned embodiment 1 is replaced by step ST3 ain which the command generating device selects an acceleration commandshape which will be mentioned later, and step ST4 of FIG. 2 is replacedby step ST4 a in which the command generating device calculates theparameter r based on the data shown in table 1 and stored in the storageunit 7.

First, a desired positioning time 2 t ₀ and a target position D for thepositioning operation of the machine 4 are inputted into the commandgenerating device 1 (in step ST1). Next, in step ST2, the vibrationfrequency ω of the machine 4 which is acquired beforehand for themachine 4 is inputted into the command generating device 1.

The command shape calculating unit 5 then, in steps ST3 a to ST4 a,determines the command shape of the position command X*(t). First, thecommand shape calculating unit 5 in accordance with this embodiment 3,in step ST3 a, uses, as an equation used for defining the accelerationcommand shape A**(t), the following equation (26):

$\begin{matrix}{{A**(t)} = \left\{ \begin{matrix}{\sin \left( {\frac{\pi}{2{rt}_{0}}t} \right)} & \left( {0 \leqq t \leqq {rt}_{0}} \right) \\1 & \left( {{rt}_{0} < t < {\left( {1 - r} \right)t_{0}}} \right) \\{\cos \left( {\frac{\pi}{2{rt}_{0}}\left( {t - {\left( {1 - r} \right)t_{0}}} \right)} \right)} & \left( {{\left( {1 - r} \right)t_{0}} \leqq t \leqq t_{0}} \right) \\{- {\sin \left( {\frac{\pi}{2{rt}_{0}}\left( {t - t_{0}} \right)} \right)}} & \left( {t_{0} < t \leqq {\left( {1 + r} \right)t_{0}}} \right) \\{- 1} & \left( {{\left( {1 + r} \right)t_{0}} < t < {\left( {2 - r} \right)t_{0}}} \right) \\{\cos \left( {\frac{\pi}{2{rt}_{0}}\left( {t - {\left( {2 - r} \right)t_{0}}} \right)} \right)} & \left( {{\left( {2 - r} \right)t_{0}} < t \leqq {2t_{0}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (26)\end{matrix}$

where r is the ratio parameter, and has a range of 0<=r<=0.5.

The command shape calculating unit 5 then calculates the ratio r whichis the parameter for specifying the acceleration command shape which isa fixed multiple of the second derivative with respect to time of theposition command according to the tabular data prestored in the storageunit 7 by using the input vibration frequency ω of the machine 4 and t₀(in step ST4 a).

FIG. 12 is a diagram showing the tabular data stored in the storage unit7. The command shape calculating unit 5, in step ST4 a, calculatest₀/vibration period=t₀ω(2π) so as to determine the parameter r accordingto table 1 shown in FIG. 12. The command shape calculating unit 5 thendetermines the acceleration command shape A**(t) from the determinedratio r according to the above-mentioned equation (26).

The associating processing unit 6 then, in step ST5, integrates theacceleration command shape A**(t) determined by the command shapecalculating unit 5 twice with respect to time, multiplies the integralresult by a constant C (i.e., a constant which makes X*(2 t ₀) be equalto D) which associates the position command at the positioning time 2 t₀ with the target position D according to the above-mentioned equation(5) so as to determine the position command X*(t).

As will be explained below, when the machine 4 performs the positioningoperation, the machine 4 can be made to operate in response to theposition command X*(t) generated according to the above-mentionedprocedure without any vibration being excited at the time when themachine is stopped and without any delay to the desired positioningtime. In accordance with above-mentioned embodiment 1, what is necessaryis just to find out a command shape which satisfies either of theabove-mentioned equations (16), (17), and (18), as previously explained.It is however difficult for the command generating device toanalytically find out a general command shape which satisfies either oneof the above-mentioned equations (16), (17), and (18), like that ofabove-mentioned embodiment 1.

FIGS. 13A and 13B are diagrams showing the shape of the S-curveacceleration-and-deceleration command which the command generatingdevice according to above-mentioned embodiment 1 uses. FIG. 13A shows ajerk command shape which varies during the time period from the time t=0to the time t=t₀ in a case where the positioning time is 2 t ₀, and FIG.13B shows a jerk command shape which varies during the time period fromthe time t=0 to the time t=t₀′ in a case where the positioning time is 2t ₀′ for t₀′ at which the S-curve acceleration-and-deceleration commandhas a value close to that at the time t=t₀. FIGS. 13A and 13B and theabove-mentioned equation (3) show that when the time t₀ changes t₀′, theparameter r which does not cause any vibration also changes a little ascompared with the parameter r in the case of the time t₀. This showsthat the parameter r which can suppress vibrations changes according tothe change in the positioning time 2 t ₀.

Conversely, a change in the parameter r with respect to the positioningtime 2 t ₀ which is provided to the command generating device can form acommand which can suppress vibrations. This fact is also true for notonly the command explained by above-mentioned embodiment 1 but a commandhaving a general shape. That is, a command having a command shape whichcontinuously changes depending upon a certain parameter can be changedinto a command which does not excite any vibration having a certainfrequency for a certain positioning time by changing the parametercontinuously.

Then, when it is difficult to analytically find out a command shapewhich satisfy either of the above-mentioned equations (16), (17), and(18), as mentioned above, for a certain command shape which changescontinuously depending upon a parameter like the ratio r, the commandgenerating device determines an equation showing the frequency componentof the command shape in the form dependent upon the parameter. Then, bycalculating the above-mentioned parameter which makes the equationshowing the frequency component of the command shape become 0 for acertain frequency, the command generating device can determine thecommand shape.

For example, in order to determine an equation showing the frequencycomponent of the above-mentioned equation (26), the command generatingdevice obtains the following equation (27) by carrying out a Laplacetransform of the above-mentioned equation (26).

$\begin{matrix}\begin{matrix}{{\hat{A}**(s)} = {\int_{0}^{\infty}{{A**(t)}{\exp \left( {- {st}} \right)}\ {t}}}} \\{= {\frac{B}{s^{2} + B^{2}} + {{\exp \left( {{- {rt}_{0}}s} \right)}\left( {{- \frac{s}{s^{2} + B^{2}}} + \frac{1}{s}} \right)} +}} \\{{{\exp \left( {{- \left( {1 - r} \right)}t_{0}s} \right)\left( {{- \frac{1}{s}} - \frac{s}{s^{2} + B^{2}}} \right)} +}} \\{{{{\exp \left( {{- \left( {1 + r} \right)}t_{0}s} \right)}\left( {{- \frac{1}{s}} + \frac{s}{s^{2} + B^{2}}} \right)} +}} \\{{{{\exp \left( {{- \left( {2 - r} \right)}t_{0}s} \right)}\left( {\frac{1}{s} - \frac{s}{s^{2} + B^{2}}} \right)} - {{\exp \left( {{- 2}\; t_{0}s} \right)}\frac{B}{s^{2} + B^{2}}}}\;} \\{\left( {B = {\frac{\pi}{2}\frac{1}{{rt}_{0}}}} \right)}\end{matrix} & (27)\end{matrix}$

Substitution of s=jω into the above-mentioned equation (27) (j is theimaginary unit) yields an equation showing the frequency component ofthe above-mentioned equation (26). Values of the parameter r which arenumerically determined with respect to normalized with the vibrationperiod 2π/ω and which make A**(jω) hat (hat phonetically means ̂) becomezero are table 1 which is shown in FIG. 12 and which is prestored in thestorage unit 7.

The command shape calculating unit 5 can acquire an acceleration commandshape which can suppress vibrations when selecting a value of theparameter r from this table 1. Table 1 shows only a part of thecalculation results. There are also solutions for a case wheret₀/vibration period is three or more, and these solutions can be finelystored in the storage unit 7. In the example of table 1 shown in FIG.12, values of the parameter r are determined in units of 0.05 ofto/vibration period and are stored. As an alternative, values of theparameter r can be finely determined in units of a smaller value and canbe stored in table 1.

Next, advantages offered by the present embodiment will be explainedwith reference to numerical calculation examples. Assume that thecommand generating device generates a position command for a case wherethe vibration frequency of the machine 4 is 10 Hz (ω=2π·10=31.4[rad/s]), the target position D=144, and the positioning time 2 t ₀=0.24seconds. First, the description will be directed to a numericalcalculation example to which the position command in accordance with thepresent invention is not applied, but to which a position command thatoffers a triangle-shaped velocity command which is the first derivativewith respect to time of the position command is applied. In thenumerical calculation examples which will be mentioned below, theposition, velocity, and acceleration are expressed in the form ofdimensionless quantity.

FIGS. 14A and 14B are graphs showing the numerical calculation exampleto which the position command of the present invention is not applied,but to which a triangle-shaped velocity command is applied. FIG. 14Ashows the machine's position when a position command which offers thetriangle-shaped velocity command is applied to the actuator drivecontrol device 2, and FIG. 14B shows the machine's velocity when thetriangle-shaped velocity command is applied to the actuator drivecontrol device 2. A curve shown by a broken line of FIG. 14A indicatesthe position command, and a solid line of FIG. 14A indicates themachine's position. A curve shown by a broken line in FIG. 14B indicatesthe velocity command, and a solid line of FIG. 14B indicates themachine's velocity.

In the case of the position command to which the present invention isnot applied, a large residual vibration occurs after the positioningtime 0.24 seconds and the settling characteristics get worse, as can beseen from the waveform of the machine's velocity shown in FIG. 14B. Inaddition, the waveform of the machine's position in FIG. 14A shows thatthe vibration occurs after the positioning time 0.24 seconds.

Next, a numerical calculation example will be explained for a case wherean acceleration command shape defined by the above-mentioned equation(26) is used, while the ratio parameter r is determined (r=0.4) withoutusing table 1 of FIG. 12. FIGS. 15A and 15B are graphs showing anumerical calculation example in a case where an acceleration commandhaving a trapezoidal shape is applied according to the above-mentionedequation (26), and the ratio parameter r=0.4. FIG. 15A shows arelationship between the position command and the machine's position,and FIG. 15B shows a relationship between the velocity command and themachine's velocity. A curve shown by a broken line of FIG. 15A indicatesthe position command, and a solid line of FIG. 15A indicates themachine's position. A curve shown by a broken line of FIG. 15B indicatesthe velocity command, and a solid line of FIG. 15B indicates themachine's velocity.

It is apparent from FIG. 15B that although the use of the accelerationcommand shape defined by the above-mentioned equation (26) makes thevelocity command be smoother than the velocity command of FIG. 14B, aresidual vibration occurs after the positioning time 0.24 seconds evenif the machine 4 performs the positioning operation according to theposition command having this shape, and therefore the settlingcharacteristics get worse. It can be therefore understood that onlysmoothing the acceleration command shape does not prevent vibrationssufficiently.

Next, a numerical calculation example in a case where the command shapeis determined according to the above-mentioned procedure of theflowchart shown in FIG. 11 will be explained. FIGS. 16A and 16B aregraphs showing a numerical calculation example in a case where thecommand shape is determined by the processing in accordance withembodiment 3. FIG. 16A shows a relationship between the position commandand the machine's position, and FIG. 16B shows a relationship betweenthe velocity command and the machine's velocity. A curve shown by abroken line of FIG. 16A indicates the position command, and a solid lineof FIG. 16A indicates the machine's position. A curve shown by a brokenline of FIG. 16B indicates the velocity command, and a solid line ofFIG. 16B indicates the machine's velocity.

In the example of FIGS. 16A and 16B, the ratio r=0.23 is determined fromtable 1 shown in FIG. 12 according to the procedure shown in FIG. 11,and a position command having an acceleration command shape which iscalculated using the parameter r according to the above-mentionedequation (26) is provided. It is apparent from the waveforms shown inFIGS. 16A and 16B that the machine reaches the target position at thepositioning time 0.24 seconds, and no residual vibration occurs in themachine after the positioning time 0.24 seconds. The command shapegenerated in accordance with this embodiment makes it possible for themachine to complete the positioning operation without any delay to thedesired positioning time.

FIG. 17 is a diagram showing the acceleration command shape A**(t) whichis calculated by the processing in accordance with embodiment 3. Thecurve of the acceleration command shape as shown in FIG. 17 which isdefined by the above-mentioned equation (26) is called a deformedtrapezoidal curve. Since this acceleration command shape which is adeformed trapezoidal curve is continuous, the present embodiment offersan advantage of being able to soften shocks at the time of actuation ofthe machine. In addition to this advantage, this embodiment offers anadvantage of being able to prevent vibrations from occurring in themachine.

As mentioned above, the command generating device in accordance withthis embodiment 3 is provided with the storage unit 7 for establishingan equation showing the frequency component of a command shape signalincluding the parameter for specifying the shape of a position command,the frequency component being dependent upon a change in the parameter,for calculating a frequency at which the equation becomes equal to zerodependently upon the change in the parameter in advance, and for storingtabular data showing a correspondence between this parameter, and boththe frequency at which the equation indicating the frequency componentof the command shape signal becomes equal to zero and a positioningtime, and the command shape calculating unit 5 determines the commandshape using the tabular data stored in the storage unit 7. Therefore,the command generating device can obtain the position command which cansuppress vibrations without performing complicated calculations usingthe command shape calculating unit 5.

The command generating device in accordance with this embodiment 3 usesan acceleration command shape signal having a value which is equal to afixed multiple of the acceleration command which is the secondderivative with respect to time of the position command as the commandshape signal, as previously mentioned. As an alternative, the commandgenerating device in accordance with this embodiment 3 can use an nthderivative command shape signal having a value which is equal to a fixedmultiple of the nth derivative with respect to time of the positioncommand, as the command shape signal. In this case, the same advantageis provided.

Since the shape of the acceleration command is continuous and verticaldisplacements of the acceleration command shape are not rapid, thecommand shape seldom includes high-frequency signals. For this reason,the command generating device in accordance with this embodiment can beapplied to even actuators and actuator drive control devices havingnot-so-good responsibility. In addition, the present embodiment offersanother advantage of making it possible for the machine to complete thepositioning operation of positioning the machine's final positionwithout any delay to the desired positioning time 2 t ₀.

The command generating device 1 of this embodiment has only to calculatea relationship between a value which is obtained by normalizing the timevariable t₀ with the vibration period, and the parameter r whichsuppresses vibrations, and to have the storage unit 7 for storingtabular data showing the relationship, as shown in FIG. 12. Whengenerating the position command, the command generating device 1 of thisembodiment has only to calculate the parameter r from t₀ and ω which areinputted thereto using the storage unit 7. Therefore, the commandgenerating device 1 in accordance with this embodiment can generate theposition command without carrying out any complicated calculations.Therefore, the command generating device in accordance with thisembodiment 3 is especially suitable for a case where much time cannot bespent on the command generation processing, such as a case where anotherpositioning time and another target position are provided immediatelyand positioning control is carried out using the other positioning timeand other target position after one positioning control has beencompleted. As can be seen from the above description, the commandgenerating device in accordance with this embodiment 3 can beimplemented without having to use any expensive processor or the like.

Embodiment 4

Although a command generating device in accordance with this embodiment4 has the same structure as that according to above-mentioned embodiment3 basically, the command generating device in accordance with thisembodiment 4 differs from that according to above-mentioned embodiment 3in that a command shape calculating unit calculates an accelerationcommand shape which can prevent vibrations with respect to a time t₀which is shorter than the period T of a vibration which occurs in atarget machine to be driven.

FIG. 18 is a diagram showing the acceleration command shape a**(t) whichis generated by command shape calculating unit in accordance withembodiment 4 and which lasts from the time t=0 to the time t=t₀. Theacceleration command shape a**(t) which lasts throughout the time periodfrom the time t=0 to the time t=t₀ during which vibrations can beprevented is shown for the case where to is shorter than the vibrationperiod of the machine. Since the left part of the above-mentionedequation (17) can be expressed like the following equation (28), settingthe equation (17) to 0 is equivalent to setting the following equation(28) to 0. As shown in FIG. 18, it is determined that a**(t) should havea shape which globally decreases during the time period from the timet=0 to the time t=t₀ in order that the above-mentioned equation can besatisfied.

∫₀ ⁰ sin ω(t ₀−τ)a*(τ)dτ=∫ ₀ ⁰ sin ω(τ)a*(t ₀−τ)dτ  (28)

In accordance with this embodiment 4, the following equation (29) can beprovided as a candidate for the acceleration command shape A**(t).

$\begin{matrix}{{A**(t)} = \left\{ \begin{matrix}{\cos \left( {\frac{\pi}{2}\frac{r}{t_{0}}t} \right)} & \left( {0 \leqq t \leqq t_{0}} \right) \\{- {\cos \left( {\frac{\pi}{2}\frac{r}{t_{0}}\left( {{2t_{0}} - t} \right)} \right)}} & \left( {t_{0} \leqq t \leqq {2\; t_{0}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (29)\end{matrix}$

where r is a parameter and the command shape can be changed by changingthe parameter r.

A Laplace transform of the acceleration command shape A**(t) which isexpressed by the above-mentioned equation (29) and which includes theparameter r yields the following equation (30). Here, ω which makesA**(jω) hat (hat phonetically means ̂) become 0 is given by thefollowing equation (31). Therefore, when the vibration frequency ω ofthe machine and a desired positioning time 2 t ₀ are provided, theparameter r is given by the following equation (32), and the parameter rcan be determined according to this equation.

$\begin{matrix}{{{\hat{A}**(s)} = {\frac{s}{s^{2} + B^{2}}\left( {1 - {2\; \cos \; {Bt}_{0}{\exp \left( {{- t_{0}}s} \right)}} + {\exp \left( {{- 2}\; t_{0}s} \right)}} \right)}}{B = \frac{\pi \; r}{2\; t_{0}}}} & (30) \\{\omega = {\left( {{\pm \frac{r}{2}} + {2\mspace{20mu} m}} \right)\pi \times \frac{1}{t_{0}}\left( {m\text{:}\mspace{14mu} {integer}\mspace{14mu} {equal}\mspace{14mu} {to}\mspace{14mu} {or}\mspace{14mu} {larger}\mspace{14mu} {than}\mspace{14mu} 1} \right)}} & (31) \\{r = {{\pm 2}\left( {\frac{\omega \; t_{0}}{\pi} - {2\mspace{20mu} m}} \right)}} & (32)\end{matrix}$

There is a degree of freedom in each of the variable m and selection ofthe positive and negative signs ± in the above-mentioned equation (32).FIG. 19 is a diagram showing tabular data (referred to as table 2 fromhere on) stored in a storage unit of the command generating device inaccordance with embodiment 4. In the above-mentioned equation (32), thevariable m is determined and the positive or negative sign is selectedso that the parameter r becomes as small as possible. The parameter r isthen calculated for a variable which is obtained by normalizing the timevariable t₀ with the vibration period (i.e., a value which is calculatedby dividing t₀ by the vibration period), and is stored in table 2.

When the vibration frequency ω of the machine 4 and positioning time 2 t₀ are input to the command generating device in accordance with thisembodiment 4, the command shape calculating unit 5 calculatesto/vibration period=t₀ω/(2π) so as to determine the parameter r based oneither the data of table 2 shown in FIG. 19 and stored in the storageunit 7 or the above-mentioned equation (32). The command shapecalculating unit 5 then determines the acceleration command shape fromthis parameter r according to the above-mentioned equation (29). Thecommand shape calculating unit 5 can thus calculate the accelerationcommand shape A**(t) according to the procedure so as to obtain acommand which does not excite any vibration in the machine.

When using the acceleration command shape expressed by theabove-mentioned equation (29), step ST3 a of the flowchart of FIG. 11which is explained in above-mentioned embodiment 3 is replaced by aprocess of “using the above-mentioned equation (29), as the equationwhich defines the acceleration command shape A**(t)”, and step ST4 a isreplaced by a process of “calculating the parameter r from table 2 basedon ω and t₀.”

FIG. 20 is a diagram showing an example of the acceleration commandshape generated by the processing in accordance with embodiment 4, andshows the acceleration command shape which is expressed by theabove-mentioned equation (29). As shown in the figure, the accelerationcommand shape A**(t) which is expressed by the above-mentioned equation(29) changes smoothly, but does not change so sharply during anacceleration time period (i.e., a time period from the time t=0 to thetime t=t₀).

As mentioned above, the command generating device in accordance withthis embodiment 4 includes the storage unit 7 that defines anacceleration command shape signal, which has a value equal to a fixedmultiple of the second derivative with respect to time of the positioncommand and has an acceleration command value pattern which is specifiedby a parameter r and which changes continuously with time, as cos(πrt/(2t ₀)) for the time period from the time t=0 to the time t=t₀, as−cos(πr(2 t ₀−t)/(2 t ₀)) for the time period from the time t=t₀ to thetime t=2 t ₀, and as 0 for other time periods, as expressed by theabove-mentioned equation (29), also defines the above-mentioned equation(31) showing the frequency component of the acceleration command shapesignal depending on said parameter r, calculates the frequencies atwhich the frequency component of the acceleration command shape signalbecomes equal to zero dependently upon the parameter r, and stores theparameter r, frequencies at which the frequency component of theacceleration command shape signal becomes equal to zero, and positioningtime therein while associating them with one another, and the commandshape calculating unit 5 that reads a parameter r corresponding to afrequency at which the frequency component of the acceleration commandshape signal becomes equal to zero for the frequency ω of a vibrationwhich occurs in the machine 4 from the storage unit 7, and calculates aposition command which can prevent vibrations for the positioning time 2t ₀, the time t₀ being shorter than the vibration period of the machine4, by using the parameter r. Since the acceleration command is smoothduring the acceleration time period (0<=t<=t₀) and is not changed sosharply, many high-frequency components are not contained in theacceleration command. Therefore, vibrations resulting fromhigh-frequency components are hard to excite, as explained inabove-mentioned embodiment 1.

The use of the acceleration command shape expressed by theabove-mentioned equation (29) makes it possible for the machine tocomplete the operation of positioning the machine's final positionwithout any delay to the desired positioning time 2 t ₀. The commandgenerating device need not carry out complicated repetitive calculationsetc. in order to obtain the position command. As can be seen from theabove description, the command generating device in accordance with thisembodiment 4 can be implemented without having to use any expensiveprocessor or the like.

It is undoubted that various shape commands can be provided as a commandhaving a command shape which continuously changes dependently upon acertain parameter, instead of the command shape shown in theabove-mentioned embodiment. For example, either a cam curve or a splinecurve having a shape which continuously changes dependently upon acertain parameter can be used as the command shape.

The command generating device in accordance with any of above-mentionedembodiment 3 and 4 generates the position command using the accelerationcommand shape which is equal to a fixed multiple of the secondderivative with respect to time of the position command, as previouslyexplained. As an alternative, the command generating device inaccordance with any of above-mentioned embodiment 3 and 4 can apply theabove-mentioned concept of this embodiment to an nth derivative commandshape which is equal to a fixed multiple of the nth derivative withrespect to time of the position command, the nth derivative commandshape being different from the acceleration command shape (i.e., n>=3),and can calculate the nth derivative command shape so as to generate theposition command.

In addition, since the command shape which is shown in any ofabove-mentioned embodiments 1 to 3, as the position command obtained inaccordance with the present invention, is known, the position commanddoes not has a shape unsuitable for the positioning operation, such as ashape which causes the target machine to pass the target position onceand to move backward and reach the target position during the timeperiod from the time t=0 to the time t=the positioning time.

Embodiment 5

It is necessary to carry out positioning control of two or more targetpositions at corresponding positioning times, respectively, depending onthe type of a target machine to be driven. For example, there is a casewhere a target position D₁ of a certain machine to be driven ispositioned at a positioning time t₀₁, and another target position D₂ ofthe machine is then positioned at another positioning time t₀₂. It ispreferable to position such a machine to be driven using a parameterwhich is suitable for prevention of vibrations at every positioningtime. Furthermore, different command shapes are provided for a pluralityof positioning times, respectively, and are combined and used.

For example, an acceleration command shape which is expressed by theabove-mentioned equation (29) is used for a case of t₀<(2π)/ω, while anacceleration command shape which is a trapezoid, that is, which isexpressed by the above-mentioned equations (1) and (2) is used for acase of t₀>=(2π)/ω.

That is, a command shape calculating unit 5 in accordance with thisembodiment 5 stores, for example, information about command shapesexplained in above-mentioned embodiments in a storage unit 7, and readsan appropriate command shape according to a selected positioning time soas to determine a command shape. In other words, the command shapecalculating unit 5 uses difference command shapes for differentpositioning times. As a result, the command generating device inaccordance with this embodiment 5 can acquire a command shape which doesnot excite any vibration for an arbitrarily-given positioning time. Itshould be understood that the command generating device in accordancewith the present embodiment uses a combination of various commandshapes, instead of the above-mentioned combination of the command shapeexpressed by the above-mentioned equation (29) and that expressed by theabove-mentioned equations (1) and (2).

Embodiment 6

Although a command generating device in accordance with this embodiment6 has the same structure as that according to above-mentioned embodiment1 or 3 basically, the command generating device in accordance with thisembodiment 6 differs from those according to above-mentioned embodiments1 and 3 in that the command generating device of this embodiment 6calculates a position command in consideration of damping of a vibrationwhich occurs in a target machine to be driven, as well as the frequencyof the vibration, a positioning time, and a target position.

Next, the operation of the command generating device in accordance withthis embodiment of the present invention will be explained. FIG. 21 is aflowchart showing a process of calculating a position command which iscarried out by the command generating device in accordance withembodiment 6. This figure shows an example of a procedure for obtainingthe position command X*(t) which can prevent vibrations for both a casewhere there is a large amount of vibration damping and a case wherethere is a sufficiently small amount of vibration damping.

First, a desired positioning time 2 t ₀ and a target position D whichare used for the positioning operation of the machine 4 are inputtedinto the command generating device 1 in accordance with embodiment 6 (instep ST1 b). Next, the frequency ω of a vibration which can occur in themachine 4 and the vibration damping coefficient ζ for this vibrationwhich are calculated in advance for the machine 4 are inputted to thecommand generating device 1 (in step ST2 b). The vibration dampingcoefficient ζ can be calculated from two or more maximum values of theamplitude of the residual vibration.

A command shape calculating unit 5 of the command generating device 1 inaccordance with embodiment 6 then selects a command shape from aplurality of command shape candidates (in step ST3 b). For example, byusing the process of determining a command shape which is shown ineither of above-mentioned embodiments 1 to 3, the command shapecalculating unit 5 selects either one of the above-mentioned equations(1), (26), and (29) so as to determine a command shape. As an example ofa rule for the selection of a command shape, there can be provided aprocess of applying an acceleration command shape which is expressed bythe above-mentioned equation (29) in a case of t₀<2π/ω, and applying ajerk command shape which is expressed by the above-mentioned equation(1) in a case of t₀>=2π/ω, with respect to the vibration period 2π/ω ofthe machine, as explained in above-mentioned embodiment 5.

The command shape calculating unit 5 then, in step ST4 b, calculatest₀ω/(2π) from ω and t₀, and determines a parameter r from the valuet₀ω/(2π) according to an equation, such as the above-mentioned equation(3) or the above-mentioned equation (32), or using a table, such asabove-mentioned table 1 or 2, stored in a storage unit 7. After that,the command shape calculating unit 5 calculates an nth derivativecommand shape X**^((n))(t) which is equal to a fixed multiple of the nthderivative with respect to time of the position command from theparameter r.

When the processing including up to the above-mentioned step iscompleted, the command shape calculating unit 5 determines whether ornot the vibration damping coefficient ζ of the machine is sufficientlysmall (in step ST5 b). For example, the command shape calculating unit 5determines whether or not the vibration damping coefficient ζ is about0. When determining that the vibration damping coefficient ζ of themachine is sufficiently small, the command generating device shifts to aprocess of step ST6 b in which an associating processing unit 6integrates the nth derivative command shape X**^((n))(t) which isobtained from the position command and which is expressed by, forexample, the above-mentioned equation (5), n times with respect to time,and multiplies the integral result by a constant which associates theposition command at the positioning time 2 t ₀ with the target positionso as to determine the position command X*(t).

On the other hand, when determining that the vibration dampingcoefficient ζ of the machine is not sufficiently small, the commandgenerating device shifts to a process of step ST7 b in which the commandshape calculating unit 5 integrates the nth derivative command shapeX**^((n))(t) which is obtained from the position command (n−1) timeswith respect to time so as to determine a first velocity command shapeV**(t) bar (bar phonetically means ⁻). The command shape calculatingunit 5 then calculates a second velocity command shape V**(t) bymultiplying the first velocity command shape V**(t) bar (barphonetically means ⁻) by the following equation (33) (in step ST8 b).The associating processing unit 6 then, in step ST9 b, integrates avelocity command shape V**(t) which is equal to a fixed multiple of thevelocity command which is the first derivative with respect to time ofthe position command once with respect to time, and multiplies theintegral result by a constant which associates the position command atthe positioning time 2 t ₀ with the target position. That is, theassociating processing unit obtains the position command X*(t) accordingto the following equation (34):

$\begin{matrix}{\exp\left( {{- \zeta}\frac{\omega}{\sqrt{1 - \zeta^{2}}}t} \right)} & (33) \\{{X*(t)} = {\frac{D}{\int_{0}^{2t\; 0}{{V**(\tau)}\ {\tau}}} \times {\int_{0}^{tt}{{V**(\tau)}\ {\tau}}}}} & (34)\end{matrix}$

The command generating device can prevent vibrations having dampingusing the position command X*(t) which is generated according to theabove-mentioned procedure, as will be mentioned below. An expression forobtaining the machine's final position X(t) from the position commandX*(t) which is thus determined from the vibration frequency ω andvibration damping coefficient ζ of the machine is given by the followingequation (35). Similarly, an expression for obtaining the machine'sfinal velocity V (t) from the velocity command V*(t) is given by thefollowing equation (36). When this relationship is rewritten into one inthe form of time domain using the following equation (37) showing theimpulse response of a transfer function: ω₀ ²/(s²+2ζω₀s+ω₀ ²), and aresponse after the positioning time, i.e., a response at a time t>=2 t₀, is described, the following equation (38) is obtained. Here, whenV*(t) bar (bar phonetically means ⁻) is defined by the followingequation (39), the machine's final velocity V(t) is expressed by thefollowing equation (40):

$\begin{matrix}{{{\hat{X}(s)} = {\frac{\omega_{0}^{2}}{s^{2} + {2\zeta \; \omega_{0}s} + \omega_{0}^{2}}{{\hat{X}}^{*}(s)}}}{\omega_{0} = \frac{\omega}{\sqrt{1 - \zeta^{2}}}}} & (35) \\{{\hat{V}(s)} = {\frac{\omega_{0}^{2}}{s^{2} + {2\zeta \; \omega_{0}s} + \omega_{0}^{2}}{{\hat{V}}^{*}(s)}}} & (36) \\{\frac{\omega_{0}^{2}}{\sqrt{1 - \zeta^{2}}}{{cxp}\left( {{- \zeta}\; \omega_{0}t} \right)}{\sin \left( {\omega \; t} \right)}} & (37) \\\begin{matrix}{{V(t)} = {\frac{\omega_{0}^{2}}{\sqrt{1 - \zeta^{2}}}{\int_{0}^{2t\; 0}{{cxp}\left( {{- \zeta}\; {\omega_{0}\left( {t - \tau} \right)}} \right)}}}} \\{{\sin \mspace{11mu} \omega \left( {t - \tau} \right)\ V*(\tau){t}}} \\{= {\frac{\omega_{0}^{2}}{\sqrt{1 - \zeta^{2}}}{\exp \left( {{- \zeta}\; \omega_{0}t} \right)}{\int_{0}^{2\; t\; 0}{\sin \mspace{11mu} {\omega \left( {t - \tau} \right)}}}}} \\{{V*(\tau){\exp \left( {\zeta \ \omega_{0}\tau} \right)}{\tau}}}\end{matrix} & (38) \\{{\overset{\_}{V}*(t)} = {V*(t) \times {\exp \left( {\zeta \; \omega_{0}t} \right)}}} & (39) \\{{V(t)} = {\frac{\omega_{0}^{2}}{\sqrt{1 - \zeta^{2}}}{\exp \left( {{- \zeta}\; \omega_{0}t} \right)}{\int_{0}^{2\; t\; 0}{\sin \mspace{11mu} {\omega \left( {t - \tau} \right)}\overset{\_}{V}*(\tau)\ {\tau}}}}} & (40)\end{matrix}$

As explained in above-mentioned embodiment 1, the same relationship isestablished not only for the velocity command V*(t) but for a velocitycommand shape V**(t) which is equal to a fixed multiple of the velocitycommand V*(t). In order to make the response V(t) be equal to 0 at anytime t (>=2 t ₀) after the positioning time 2 t ₀ in the above-mentionedequation (40), the command generating device calculates the nthderivative command shape X**(n)(t) which can prevent the vibrationhaving the frequency A, such as a velocity command shape, anacceleration command shape, or a jerk command shape, from the positioncommand, for a case where it is assumed that there is no vibrationdamping at the vibration frequency A, and calculates the first velocitycommand shape V**(t) bar by integrating the nth derivative command shapeX**^((n))(t) (n−1) times with respect to time.

The command shape calculating unit 5 calculates the velocity commandshape V**(t) from the velocity command shape V**(t) bar (barphonetically means ⁻), which is thus acquired, according to thefollowing equation (41). Then, in order to associate the positioncommand at the positioning time 2 t ₀ with the target position D, thecommand shape calculating unit 5 further integrates the velocity commandshape V**(t) with respect to time, and multiplies the integral result bythe constant which associates the position command at the positioningtime 2 t ₀ with the target position D so as to obtain the positioncommand X*(t). That is, the command shape calculating unit 5 obtains theposition command X*(t) according to the following equation (42):

$\begin{matrix}{{V**(t)} = {{\exp \left( {{- \zeta}\; \omega_{0}t} \right)} \times {\overset{\_}{V}**(t)}}} & (41) \\{{X*(t)} = {\frac{D}{\int_{0}^{2\; t\; 0}{{V**(\tau)}\ {\tau}}} \times {\int_{0}^{t}{{V**(\tau)}\ {\tau}}}}} & (42)\end{matrix}$

In addition, the first velocity command V**(t) bar (bar phoneticallymeans ⁻) can be multiplied by a function which can approximatef(t)=exp(−ζω₀t) during the time period [0, 2 t ₀], so as to determinethe velocity command shape V**(t). As an alternative, the first velocitycommand V**(t) bar can be multiplied by f(t)=exp (−gt) (a positiveconstant g has a value close to ζω₀), so as to determine the velocitycommand shape V**(t).

Next, advantages offered by the present embodiment will be explainedwith reference to numerical calculation examples. Assume that thecommand generating device generates a position command for a case wherethe vibration frequency of the machine 4 is 10 Hz (ω=2π·10=31.4[rad/s]), the vibration damping coefficient ζ=0.1, the target positionD=15.0, and the positioning time 2 t ₀ is 0.18 seconds. First, thedescription will be directed to a numerical calculation example to whichthe position command in accordance with the present embodiment is notapplied, but to which a triangle-shaped velocity command is applied.FIGS. 22A to 22C are graphs showing the numerical calculation example towhich the position command in accordance with the present embodiment isnot applied, but to which a position command which offers atriangle-shaped velocity command is applied. FIG. 22A is a graph showingthe position command and the machine's position, FIG. 22B is an enlargedview of FIG. 22A, and FIG. 22C is a graph showing the velocity commandand the machine's velocity. Solid lines shown in FIGS. 22A and 22Bindicate the machine's position, and dotted lines indicate the positioncommand. A solid line shown in FIG. 22C indicates the machine'svelocity, and a dotted line indicates the velocity command which is thefirst derivative with respect to time of the position command. As can beseen from FIGS. 22B and 22C, in the case of the position command whichoffers a triangle-shaped velocity command, a large residual vibrationoccurs after the positioning time 0.18 seconds.

Next, a numerical calculation example in which a position command inaccordance with this embodiment is applied will be explained. FIGS. 23Ato 23C are graphs showing the numerical calculation example in which theposition command in accordance with this embodiment 6 is applied. FIG.23A is a graph showing the position command and the machine's position,FIG. 23B is an enlarged view of FIG. 23A, and FIG. 23C is a graphshowing the velocity command and the machine's velocity. Solid linesshown in FIGS. 23A and 23B indicate the machine's position, and dottedlines indicate the position command. A solid line shown in FIG. 23Cindicates the machine's velocity, and a dotted line indicates thevelocity command which is the first derivative with respect to time ofthe position command. As can be seen from FIGS. 23B and 23C, in the caseof the position command in accordance with the present embodiment, noresidual vibration occurs after the positioning time 0.18 seconds.

As mentioned above, in the command generating device in accordance withthis embodiment 6, the command shape calculating unit 5 calculates anacceleration command shape signal having a value which is equal to afixed multiple of an acceleration command so that a convolution of theimpulse response of a transfer function which is determined from thefrequency ω of a vibration which occurs in the machine 4, theconvolution being calculated over the time period from the positioningtime onward, and a velocity command which is the first derivative withrespect to time of a position command becomes equal to zero, calculatesa first velocity command shape signal by integrating the accelerationcommand shape signal once with respect to time, and calculates avelocity command shape signal having a value which is equal to a fixedmultiple of the first derivative with respect to time of the positioncommand by multiplying the first velocity command shape signal by afunction exp(−(ζωt)/(1−ζ²)^(1/2)), where ζ is the vibration dampingcoefficient of the machine and t is a time. Therefore, the commandgenerating device can generate the position command in consideration ofthe vibration damping of the machine 4. The command generating devicecan provide a command which can suppress vibrations even to a machine inwhich a vibration having a relatively large amount of damping occurs.

Embodiment 7

In either of above-mentioned embodiments 1 to 6, an example ofgenerating a position command for moving a target machine to be drivenfrom a certain position to a target position is explained. In contrast,a command generating device in accordance with this embodiment 7generates either a velocity command for changing the velocity of atarget machine to be driven from a certain velocity to another velocity,or an acceleration command for changing the acceleration of the machinefrom a certain acceleration to another acceleration, by using the sameconcept.

FIG. 24 is a block diagram showing an example of the structure of asystem for actuating and controlling the machine, to which the commandgenerating device in accordance with embodiment 7 of the presentinvention is applied. When generating a velocity command V*(t), thecommand generating device 1 calculates an nth derivative command shapesignal having a value which is equal to a fixed multiple of the nthderivative with respect to time of the velocity command V*(t) so that aconvolution of the impulse response of a transfer function which isdetermined from the vibration frequency ω and vibration dampingcoefficient ζ of the machine 4 and an acceleration command A*(t) whichis the first derivative with respect to time of the velocity commandV*(t) becomes equal to zero, the convolution being calculated over thetime period from a positioning time onward. An associating processingunit 6 integrates the nth derivative command shape which is calculatedfrom the velocity command V*(t) by a command shape calculating unit 5, ntimes with respect to time, and multiplies the integral result by aconstant so as to associate the velocity command at the time when themachine 4 to be driven has a desired velocity (referred to as thevelocity transition completion time from here on) with a target velocityV₂.

Next, the operation of the command generating device in accordance withthis embodiment of the present invention will be explained. FIG. 25 is aflowchart showing an operation of generating a command which isperformed by the command generating device in accordance with embodiment7. An operation of changing the velocity of the machine from a certainvelocity to another velocity will be explained in detail with referenceto this figure. First, the time (i.e., the velocity transitioncompletion time) 2 t ₀ when the machine 4 will have the desiredvelocity, target velocity V₂, and current velocity V₁ of the machine 4are inputted to the command generating device 1 (in step ST1 c). Next,the frequency ω of a vibration which occurs in the machine 4 which isdetermined in advance is input to the command generating device 1 instep ST2 c.

The command shape calculating unit 5 of the command generating device 1in accordance with embodiment 7 then selects a velocity command shapeV**(t) including a parameter for specifying a continuous change in thevelocity command shape (in step ST3 c). To be more specific, a snapcommand shape K**(t)=k**(t)+k**(2 t ₀−t) which includes the parameter rfor specifying the shape of the command and which is equal to a fixedmultiple of the third derivative (i.e., a snap command) of the velocitycommand is determined according to the following equation (43):

$\begin{matrix}{{k**(t)} = \left\{ \begin{matrix}c & \left( {0 \leqq t \leqq {r \times t_{0}}} \right) \\0 & \left( {{r \times t_{0}} < t < {\left( {1 - r} \right) \times t_{0}}} \right) \\{- c} & \left( {{\left( {1 - r} \right) \times t_{0}} \leqq t \leqq t_{0}} \right)\end{matrix} \right.} & (43)\end{matrix}$

As an alternative, the following equation (44) is used to define a jerkcommand shape J**(t) which includes the parameter r for specifying theshape of the above-mentioned command and is equal to a fixed multiple ofthe second derivative with respect to time of the velocity command.

$\begin{matrix}{{J^{**}(t)} = \left\{ \begin{matrix}{\sin \left( {\frac{\pi}{2\; {rt}_{0}}t} \right)} & \left( {0 \leqq t \leqq {rt}_{0}} \right) \\1 & \left( {{rt}_{0} < t < {\left( {1 - r} \right)t_{0}}} \right) \\{\cos \left( {\frac{\pi}{2\; {rt}_{0}}\left( {t - {\left( {1 - r} \right)t_{0}}} \right)} \right)} & \left( {{\left( {1 - r} \right)t_{0}} \leqq t \leqq t_{0}} \right) \\{- {\sin \left( {\frac{\pi}{2\; {rt}_{0}}\left( {t - t_{0}} \right)} \right)}} & \left( {t_{0} < t \leqq {\left( {1 + r} \right)t_{0}}} \right) \\{- 1} & \left( {{\left( {1 + r} \right)t_{0}} < t < {\left( {2 - r} \right)t_{0}}} \right) \\{\cos \left( {\frac{\pi}{2\; {rt}_{0}}\left( {t - {\left( {2 - r} \right)t_{0}}} \right)} \right)} & \left( {{\left( {2 - r} \right)t_{0}} < t \leqq {2\; t_{0}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (44)\end{matrix}$

The following equation (45) is used to define another jerk commandJ**(t) including the parameter r.

$\begin{matrix}{{J^{**}(t)} = \left\{ \begin{matrix}{\cos \left( {\frac{\pi \; r}{2\; t_{0}}t} \right)} & \left( {0 \leqq t \leqq t_{0}} \right) \\{- {\cos \left( {\frac{\pi \; r}{2\; t_{0}}\left( {{2\; t_{0}} - t} \right)} \right)}} & \left( {t_{0} \leqq t \leqq {2\; t_{0}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (45)\end{matrix}$

Then, the command shape calculating unit 5 calculates the parameter rbased on the inputted vibration frequency 6 of the machine 4 and time t₀(in step ST4 c). To be more specific, when using the above-mentionedequation (43) as the command shape, the command shape calculating unit 5determines the parameter r based on the above-mentioned equation (3).When using the above-mentioned equation (44), the command shapecalculating unit 5 determines the parameter r based on table 1 shown inFIG. 12 and stored in a storage unit 7. When using the above-mentionedequation (44), the command shape calculating unit 5 can alternativelydetermine the parameter r based on table 2 shown in FIG. 19 and storedin the storage unit 7. When the above-mentioned equation (43) is used inorder to determine the nth derivative command shape signal from thevelocity command, n=3. When the above-mentioned equation (43) or (45) isused in order to determine the nth derivative command shape signal fromthe velocity command, n=2.

In step ST5 c, the associating processing unit 6 integrates the nthderivative command shape signal, which is obtained from the velocitycommand in the above-mentioned step, n times with respect to time, andthen obtains a velocity command V*(t) by multiplying the integral resultby a constant which associates the velocity command at the velocitytransition completion time with the target velocity V₂ (i.e., a constantfor making V*(2 t ₀) be equal to V₂). For example, when the commandshape is a jerk command shape, the associating processing unit performsthe processing using the following equation (46). When the command shapeis a snap command shape, the associating processing unit performs theprocessing using the following equation (47). The above-mentionedequations (46) and (47) show the calculation expressions which are usedfor calculating the velocity command V*(t) when the jerk command shapewhich is the second derivative command shape signal obtained from thevelocity command, and the snap command shape which is the thirdderivative command shape signal obtained from the velocity command areused as the nth derivative command shape signal, respectively. On theother hand, when the command shape is another nth derivative commandshape signal which is obtained from the velocity command, theassociating processing unit performs roughly the same processing.

$\begin{matrix}{{V^{*}(t)} = {{\frac{V_{2} - V_{1}}{\int_{0}^{2\; t\; 0}{\int_{0}^{\tau \; 1}{{J^{*}(\tau)}\ {\tau}\ {\tau_{1}}}}} \times {\int_{0}^{1}{\int_{0}^{\tau \; 1}{{J^{*}(\tau)}\ {\tau}\ {\tau_{1}}}}}} + V_{1}}} & (46) \\{{V^{*}(t)} = {{\frac{V_{2} - V_{1}}{\int_{0}^{2\; t\; 0}{\int_{0}^{\tau \; 2}{\int_{0}^{\tau \; 1}{{K^{*}\ (\tau)}{\tau}\ {\tau_{1}}\ {\tau_{2}}}}}} \times {\int_{0}^{1}{\int_{0}^{\tau \; 2}{\int_{0}^{\tau \; 1}{{K^{*}(\tau)}\ {\tau}{\tau_{1}}{\tau_{2}}}}}}} + V_{1}}} & (47)\end{matrix}$

By applying the velocity command V*(t) which the command generatingdevice thus generates according to the above-mentioned procedure to anactuator drive control device 2, the command generating device canchange the velocity of the machine 4 from the certain velocity V₁ to theother velocity V₂ without exciting any vibration in the machine 4 whenthe machine 4 performs the positioning operation. Next, the procedurewill be explained in detail.

First, consider the velocity command for changing the velocity of themachine 4 from the current velocity V₁ to the target velocity V₂ duringthe time period from the time t=0 to the time t=2 t ₀ without excitingany vibration in the machine 4. As in the case of the position andvelocity commands, the following equation (48) is established betweenA*(s) hat (hat phonetically indicates ̂) which is a Laplace transform ofthe acceleration command A*(t), and A(s) hat (hat phonetically indicateŝ) which is a Laplace transform of the machine's final accelerationA(t). Rewriting the equation (48) into one in the form of time domainyields the following equation (49). Assume that the acceleration commandA*(t) which is the first derivative with respect to time of the velocitycommand is expressed by the following equation (50), and has asymmetrical shape with respect to the time t=t₀. Further assume thata*(t) has a relationship given by the following equation (51):

$\begin{matrix}{{\hat{A}(s)} = {\frac{\omega^{2}}{s^{2} + \omega^{2}}{{\hat{A}}^{*}(s)}}} & (48) \\{{A(t)} = {\int_{0}^{1}{\sin \; {\omega \left( {t - \tau} \right)}{A(\tau)}\ {\tau}}}} & (49) \\{{A^{*}(t)} = {{a^{*}(t)} + {a^{*}\left( {{2\; t_{0}} - t} \right)}}} & (50) \\{{a^{*}(t)}\left\{ \begin{matrix}{\neq 0} & \left( {0 \leqq t \leqq t_{0}} \right) \\{= 0} & ({otherwise})\end{matrix} \right.} & (51)\end{matrix}$

At this time, the jerk command J*(t) which is the second derivative withrespect to time of the velocity command, and the snap command K*(t)which is the third derivative with respect to time of the velocitycommand are given by the following equations (52) and (53),respectively:

J*(t)=j*(t)−j*(2t ₀ −t)  (52)

K*(t)=k*(t)+k*(2t ₀ −t)  (53)

where j*(t)=da*(t)/dt and k*(t)=dj*(t)/dt.

When A(t)=0 is established after the positioning time (t>=2 t ₀), themachine 4 continues moving at a certain velocity after the positioningtime without vibrating. Then, substitution of the above-mentionedequations (50), (52), and (53) into the above-mentioned equation (49)yields the following equation (54):

$\begin{matrix}\begin{matrix}{{A(t)} = {\int_{0}^{2\; t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}\left\{ {a^{*}\left( {{2\; t_{0}} - \tau} \right)} \right\} \ {\tau}}}} \\{= {{\int_{0}^{t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}{a^{*}(\tau)}\ {\tau}}} +}} \\{{\int_{0}^{2t\; 0}{\sin \; {\omega \left( {t - \tau} \right)}{a^{*}\left( {t - {2\; t_{0}} - \tau} \right)}\ {\tau}}}} \\{= {2\; \sin \; {\omega \left( {t - t_{0}} \right)}{\int_{0}^{t\; 0}{\cos \; {\omega \left( {t_{0} - \tau} \right)}{a^{*}(\tau)}\ {\tau}}}}} \\{= {\frac{2}{\omega}\sin \; {\omega \left( {t - t_{0}} \right)}{\int_{0}^{t\; 0}{\sin \; {\omega \left( {t_{0} - \tau} \right)}{j^{*}(\tau)}\ {\tau}}}}} \\{= {\frac{2}{\omega^{2}}\sin \; {\omega \left( {t - t_{0}} \right)}\begin{Bmatrix}{\left( {{j^{*}\left( t_{0} \right)} - {\cos \; \omega \; t_{0}{j^{*}(0)}}} \right) -} \\{\int_{0}^{t\; 0}{\cos \; {\omega \left( {t_{0} - \tau} \right)}{k^{*}(\tau)}\ {\tau}}}\end{Bmatrix}}}\end{matrix} & (54)\end{matrix}$

It is apparent from the above-mentioned equation (54) that anacceleration command a*(t), a jerk command j*(t), and a snap commandk*(t) which satisfy at least one of the following equations (55), (56),and (57) have only to be formed in order that A(t)=0 can be establishedafter the positioning time t>=2 t ₀. This formation can be carried outaccording to a procedure similar to the procedure for forming a velocitycommand, an acceleration command, and a jerk command in the case ofpositioning the machine from a certain position to a target position.

∫₀ ^(t0) cos ω(t ₀−τ)a*(τ)dτ=0  (55)

∫₀ ⁰ sin ω(t ₀−τ)j*(τ)dτ=0  (56)

∫₀ ⁰ cos ω(t ₀−τ)k*(τ)dτ=0, j*(t ₀)−cos ωt₀ j*(0)=0  (57)

The above-mentioned equations (55), (56), and (57) correspond to theabove-mentioned equations (13), (14), and (15) shown in above-mentionedembodiment 1, respectively. It is clear that the same relationship isalso established among the acceleration command shape A**(t), jerkcommand shape J**(t), and snap command shape K**(t) which are equal tofixed multiples of A*(t), J*(t), and K*(t), respectively.

That is, for a certain constant k, the following equations:a**(t)=ka*(t), j**(t)=kj*(t), and k**(t)=kk*(t) are defined. Inaddition, assuming that the acceleration command shape is defined asA**(t)=a**(t)+a**(2 t ₀−t), the jerk command shape is defined asJ**(t)=j**(t)−j**(2 t ₀−t), and the snap command shape is defined asK**(t)=k**(t)+k**(2 t ₀−t), the following equations (58), (59), and (60)are established:

∫₀ ^(t0) cos ω(t ₀−τ)α***(τ)dτ=0  (58)

∫₀ ^(t0) sin ω(t ₀−τ)j**(τ)dτ=0  (59)

∫₀ ^(t0) cos ω(t ₀−τ)k**(τ)dτ=0, j**(t ₀)−cos ωt₀ j**(0)=0  (60)

Therefore, like the command generating device according to either ofabove-mentioned embodiments 1, 2, and 3 that acquires the nth derivativecommand shape which does not excite any vibration in the machine fromthe position command, the command generating device in accordance withthis embodiment can acquire the command shape which is a fixed multipleof the nth derivative with respect to time of the velocity command andwhich does not excite any vibration in the machine. As concrete examplesof the command shape, the command shapes defined by the above-mentionedequations (43), (44), and (45) can be provided. The command generatingdevice further carries out a process of integrating this command shape ntimes with respect to time, and multiplying the integral result by aconstant which associates the velocity command at the velocitytransition completion time with the target velocity V₂, i.e., theprocessing as given by the above-mentioned equations (46) and (47), soas to determine the velocity command V*(t).

Examples of the velocity command for changing the velocity of themachine from 0 to a certain velocity, which are obtained by the commandgenerating device according to above-mentioned embodiment, are shown inFIGS. 26 and 27. FIGS. 26A and 26B show the velocity command andacceleration command which is the first derivative with respect to timeof the velocity command, respectively, when k**(t) of the snap commandshape K**(t)=k**(t)+k**(2 t ₀−t) which is equal to a fixed multiple ofthe snap command which is the third derivative with respect to time ofthe velocity command is given by the above-mentioned equation (43).FIGS. 27A and 27B show the velocity command and acceleration commandwhich is the first derivative with respect to time of the velocitycommand when the jerk command shape which is equal to a fixed multipleof the jerk command which is the second derivative command of thevelocity command is given by the above-mentioned equation (45),respectively. As shown in FIGS. 26B and 27B, in both the cases, theacceleration command which is the first derivative with respect to timeof the velocity command is continuous during an acceleration timeperiod, and then rises to its peak and descends to about zero with norapid change such as a re-rise. Therefore, many high-frequencycomponents are not contained in such the acceleration command signal.

It is understood that the velocity command for changing the velocity ofthe machine from a certain velocity to another velocity without excitingany vibration in the machine is not limited to the above-mentionedcommand shape, and the velocity command can have one of various shapes,as in the case of the position command. Although the command generatingdevice in accordance with this embodiment is explained by taking, as anexample, the case where there is no damping in the vibration whichoccurs in the machine, the command generating device in accordance withthis embodiment can be also applied to cases where the vibration whichoccurs in the machine has damping, as shown in above-mentionedembodiment 6.

As mentioned above, in the command generating device in accordance withthis embodiment 7, the command shape calculating unit 5 calculates annth derivative command shape signal having a value which is equal to afixed multiple of the nth derivative with respect to time of a velocitycommand for changing the velocity of the machine 4 to a target velocityduring the time period from the time t=0 to the time t=a velocitytransition completion time so that a convolution of an accelerationcommand which is the first derivative command of the velocity command,and the impulse response of a transfer function which is determined fromthe vibration frequency ω of the machine 4 becomes equal to zero, theconvolution being calculated over the time period from the velocitytransition completion time onward, and the associating processing unit 6integrates the nth derivative command shape signal which is calculatedfrom the velocity command by the command shape calculating unit 5 ntimes with respect to time and then multiplies the integral result by aconstant for associating the velocity command at the velocity transitioncompletion with the target velocity so as to determine the velocitycommand. As a result, the command generating device can change thevelocity of the machine 4 to the target velocity without exciting anyvibration in the machine 4.

The velocity command in accordance with this embodiment can be obtainedby using nearly the same method as that used at the time of obtainingthe position command according to above-mentioned embodiments 1, and 2and 3. For this reason, the present embodiment has the same advantagesas provided by above-mentioned embodiments 1, 2, and 3 of the presentinvention. That is, the velocity command obtained by the commandgenerating device in accordance with this embodiment does not containmany high-frequency components. Therefore, the present embodiment offersan advantage of preventing excitation of vibrations in the machine dueto lack of trackability (i.e., responsibility) of the actuator 3 andactuator drive 2. Furthermore, the present embodiment offers anotheradvantage of preventing excitation of higher-order modes of vibrationsin the machine. In addition, since A(2 t ₀)=0 is established at t=thedesired velocity transition completion time 2 t ₀ in the above-mentionedequation (54), the command generating device can complete the velocitychanging operation without any delay to the desired velocity transitioncompletion time.

In above-mentioned embodiment 7, although the method of changing thevelocity of the machine from a certain velocity to a certain targetvelocity is explained, it is also possible to generate an accelerationcommand for changing the acceleration of the machine from a certainacceleration to a certain target acceleration based on the same concept.

That is, as shown in FIG. 28, the command shape calculating unit 5calculates an nth derivative command shape signal having a value whichis equal to a fixed multiple of the nth derivative with respect to timeof an acceleration command for changing the acceleration of the machine4 to a target acceleration during the time period from the time t=0 tothe time t=an acceleration transition completion time so that aconvolution of a jerk command which is the first derivative with respectto time of the acceleration command, and the impulse response of atransfer function which is determined from the vibration frequency ω ofthe machine 4 becomes equal to zero, the convolution being calculatedover the time period from the acceleration transition completion timeonward, and the associating processing unit 6 integrates the nthderivative command shape signal which is calculated from theacceleration command by the command shape calculating unit 5 n timeswith respect to time, and then multiplies the integral result by aconstant for associating the acceleration command at the accelerationtransition completion with the target acceleration so as to determinethe acceleration command A*(t). As a result, the command generatingdevice can obtain the acceleration command which does not excite anyvibration in the machine 4 when performing the acceleration changingcontrol operation on the machine 4. Since the jerk command is continuousand smooth, this variant can be applied to even the actuator 3 andactuator drive controller 2 having a low degree of trackability, andhigh-frequency vibrations are also hard to excite in the machine.

For example, the acceleration transition completion time is 2 t ₀ andthe vibration frequency of the machine is ω, the jerk command which isthe first derivative with respect to time of the acceleration command isexpressed by J*(t)=j*(t)+j*(2 t ₀−t), a crackle command shape which isequal to a fixed multiple of a crackle command which is the thirdderivative with respect to time of the acceleration command is expressedby L**(t)=1**(t)−1**(2 t ₀−t), and l**(t) is given by the followingequation (61). As an alternative, the snap command shape K**(t) whichhas a parameter r and a value equal to a fixed multiple of the snapcommand which is the second derivative with respect to time of theacceleration command is given by the following equation (62), theparameter r is determined from a table, as shown in table 1, whichassociates the parameter r with the vibration frequency ω of the machine4, and the command shape is determined. As an alternative, the snapcommand shape K**(t) is provided by the following equation (63), and theparameter r is determined from a table, as shown in table 2, whichassociates the parameter r with the vibration frequency ω of the machine4, and the command shape is determined.

$\begin{matrix}{{l^{**}(t)} = \left\{ {{\begin{matrix}c & \left( {0 \leqq t \leqq {t_{0} - t_{A}}} \right) \\0 & \left( {{t_{0} - t_{A}} < t < t_{A}} \right) \\{- c} & \left( {t_{A} \leqq t \leqq t_{0}} \right)\end{matrix}{where}\mspace{14mu} t_{A}} = {\left( {2\; {\pi/\omega}} \right)\left\lbrack {\left( {t_{0} \times \omega} \right)/\left( {2\; \pi} \right)} \right\rbrack}} \right.} & (61) \\{{K^{**}(t)} = \left\{ \begin{matrix}{\sin \left( {\frac{\pi}{2\; {rt}_{0}}t} \right)} & \left( {0 \leqq t \leqq {rt}_{0}} \right) \\1 & \left( {{rt}_{0} < t < {\left( {1 - r} \right)t_{0}}} \right) \\{\cos \left( {\frac{\pi}{2\; {rt}_{0}}\left( {t - {\left( {1 - r} \right)t_{0}}} \right)} \right)} & \left( {{\left( {1 - r} \right)t_{0}} \leqq t \leqq t_{0}} \right) \\{- {\sin \left( {\frac{\pi}{2\; {rt}_{0}}\left( {t - t_{0}} \right)} \right)}} & \left( {t_{0} < t \leqq {\left( {1 + r} \right)t_{0}}} \right) \\{- 1} & \left( {{\left( {1 + r} \right)t_{0}} < t < {\left( {2 - r} \right)t_{0}}} \right) \\{\cos \left( {\frac{\pi}{2\; {rt}_{0}}\left( {t - {\left( {2 - r} \right)t_{0}}} \right)} \right)} & \left( {{\left( {2 - r} \right)t_{0}} < t \leqq {2t_{0}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (62) \\{{K^{**}(t)} = \left\{ \begin{matrix}{\cos \left( {\frac{\pi}{2}\frac{r}{t_{0}}t} \right)} & \left( {0 \leqq t \leqq t_{0}} \right) \\{- {\cos \left( {\frac{\pi}{2}\frac{r}{t_{0}}\left( {{2t_{0}} - t} \right)} \right)}} & \left( {t_{0} \leqq t \leqq {2t_{0}}} \right) \\0 & ({otherwise})\end{matrix}\; \right.} & (63)\end{matrix}$

As explained above, the acceleration command in accordance with thisembodiment 7 can be obtained by using nearly the same method as thatused at the time of obtaining the position command according toabove-mentioned embodiments 1, 2 and 3. For this reason, the presentembodiment has the same advantages as provided by above-mentionedembodiments 1, 2, and 3 of the present invention. That is, theacceleration command obtained by the command generating device inaccordance with this embodiment does not contain many high-frequencycomponents. Therefore, the present embodiment offers an advantage ofpreventing excitation of vibrations in the machine due to lack oftrackability (i.e., responsibility) of the actuator 3 and actuator drive2. Furthermore, the present embodiment offers another advantage ofpreventing excitation of higher-order modes of vibrations in themachine.

Embodiment 8

Most of actuators have a maximum velocity which they can generate, ormost of machines have a maximum velocity at which they can move. It istherefore necessary to form a position command X*(t) which containsinformation about such a maximum velocity and which does not excite anyvibration in a target machine to be driven when the machine performs apositioning operation under such conditions.

A command generating device in accordance with this embodiment 8 forms aposition command into which information about a maximum velocity isincorporated using a velocity command for changing the velocity of thetarget machine 4 from a certain velocity to another velocity, which isdescribed in above-mentioned embodiment 7. FIG. 29 is a block diagramshowing the structure of an actuating control system for actuating andcontrolling the machine, to which the command generating device inaccordance with embodiment 8 of the present invention is applied. Thecommand generating device 1 calculates the position command X*(t) basedon a velocity transition completion time 2 t ₀, a target position D, avelocity limit V_(max), and the vibration frequency ω and vibrationdamping coefficient ζ of the machine 4, by using a velocity transitioncommand calculating unit 8 and an associating processing unit 6.

Next, the operation of the command generating device in accordance withthis embodiment of the present invention will be explained. FIG. 30 is aflowchart showing a command generating operation which is performed bythe command generating device in accordance with embodiment 8. Aprocedure for forming the position command will be explained in detailwith reference to this figure. First, the target position D, thevelocity limit V_(max) of the machine 4 to be driven, and the velocitytransition completion time (or an acceleration or deceleration timeperiod) 2 t ₀ are inputted to the command generating device 1 (in stepST1 d). Next, in step ST2 d, the vibration frequency ω of the machine 4which is determined beforehand for the machine 4 is inputted to thecommand generating device 1.

Then, based on the inputted vibration frequency ω of the machine 4, thevelocity transition command calculating unit 8 of the command generatingdevice 1 in accordance with embodiment 8 calculates a velocitytransition command V₁*(t) tilde (tilde phonetically means ˜) whichchanges the velocity of the machine 4 from zero to the velocity limitV_(max) during the time period from the time t=0 to the time t=thevelocity transition completion time (in step ST3 d). For example, asshown in above-mentioned embodiment 7, the velocity transition commandcalculating unit 8 calculates the first velocity transition commandV₁*(t) tilde using a method of generating a velocity command forchanging the velocity of the machine 4 from a certain velocity toanother velocity.

Next, the velocity transition command calculating unit 8 also calculatesa second velocity transition command V₂*(t) tilde (tilde phoneticallymeans {tilde over ( )}) which changes the velocity of the machine 4 fromthe velocity limit V_(max) to zero during the deceleration time periodof 2 t ₀ based on the inputted vibration frequency ω of the machine 4(in step ST4 d), as in the case of the process of step ST3 d.

The associating processing unit 6 then calculates the following equation(64) (in step ST5 d) so as to determine whether E is zero or more (instep ST6 d). For each velocity command value of the first velocitytransition command V₁*(t) tilde and second velocity transition commandV₂*(t) tilde, the amount of movement E which the machine 4 travelsduring the acceleration time period and deceleration time period iscompared with the target position D.

E=D−∫ ₀ ^(2t0) {tilde over (V)} ₁*(t)dt−∫ ₀ ^(2t0) {tilde over (V)}₂*(t)dt  (64)

When determining that E>=0 in step ST6 d, the associating processingunit 6 determines that the amount of travel E does not reach the targetposition D, and shifts to step ST7 d in which it calculatest₁=E/V_(max). The associating processing unit 6 then calculates avelocity command V*(t) which is the first derivative with respect totime of the position command X*(t) according to the following equation(65) (in step ST8 d). In performing this process, the associatingprocessing unit 6 inserts a command indicating the maximum velocityV_(max) between the first velocity transition command V₁*(t) tilde andthe second velocity transition command V₂*(t) tilde. In step ST9 d, theassociating processing unit 6 obtains the position command X*(t) byintegrating the velocity command V*(t) obtained in step ST8 d once withrespect to time.

$\begin{matrix}{{V^{*}(t)} = \left\{ \begin{matrix}{{\overset{\sim}{V}}_{1}^{*}(t)} & \left( {0 \leqq t \leqq {2t_{0}}} \right) \\V_{\max} & \left( {{2\; t_{0}} < t < {{2t_{0}} + t_{1}}} \right) \\{{\overset{\sim}{V}}_{2}^{*}\left( {t - {2\; t_{0}}} \right)} & \left( {{{2\; t_{0}} + t_{1}} \leqq t \leqq {{4t_{0}} + t_{1}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (65)\end{matrix}$

On the other hand, when determining that E<0 in step ST6 d, theassociating processing unit 6 determines that the amount of travel Eexceeds the target position D, and then shifts to a process of step ST10d. In step ST10 d, the associating processing unit 6 acquires a velocitycommand shape V**(t) according to the following equation (66):

$\begin{matrix}{{V^{**}(t)} = \left\{ \begin{matrix}{{\overset{\sim}{V}}_{1}^{*}(t)} & \left( {0 \leqq t \leqq {2t_{0}}} \right) \\{{\overset{\sim}{V}}_{2}^{*}\left( {t - {2\; t_{0}}} \right)} & \left( {{2t_{0}} \leqq t \leqq {4t_{0}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (66)\end{matrix}$

Then, in step ST11 d, the associating processing unit 6 integrates thevelocity command shape acquired in step ST10 d once with respect totime, and multiplies the integral result by a constant which associatesthe position command at a positioning time with the target position D.That is, the associating processing unit calculates the position commandX*(t) according to the following equation (67):

$\begin{matrix}{{X^{*}(t)} = {\frac{D}{\int_{0}^{4\; t\; 0}{{V^{**}(t)}\ {t}}} \times {\int_{0}^{t}{{V^{**}(t)}\ {t}}}}} & (67)\end{matrix}$

Next, a description will be made as to the reason why the positioncommand X*(t) can be obtained in consideration of the maximum velocityaccording to the above-mentioned procedure. First, in the case of E>=0,when the velocity command is formed so as to include the first velocitytransition command V₁*(t) tilde in order to accelerate the machine, theinserted velocity command which indicates the constant velocity ofV_(max) and which is to be provided to the machine during only the timeperiod of t1 in order to make the machine reach the target position Dafter the completion of the acceleration, and the second velocitytransition command V₂*(t) tilde in order to slow down the machine afterthe expiration of the time period of t1, the position command whichprovides an amount of travel equal to the target position D can beobtained by integrating the velocity command once with respect to time.Therefore, the velocity command which is thus obtained and is given bythe above-mentioned equation (65) does not exceed V_(max).

On the other hand, in the case of E<0, even if the machine is positionedusing the velocity command which is formed so as to include the firstvelocity transition command V₁*(t) tilde in order to accelerate themachine, and the second velocity transition command V₂*(t) tilde inorder to slowdown the machine after the completion of the acceleration,the machine is positioned past the target position D. To solve thisproblem, the velocity command shape is defined using the above-mentionedequation (66), and the velocity command shape is integrated once withrespect to time, as shown in the above-mentioned equation (67), and theintegral result is multiplied by the constant which associates theposition command at the positioning time with the target position D, sothat the position command which properly positions the machine can bedetermined.

The velocity command V*(t) which is the first derivative with respect totime of the position command X*(t) at this time is given by thefollowing equation (68). When shifting to step ST10 d, the followinginequality D/(D−E)<1 is established since E<0, and the velocity commandV*(t) does not exceed the maximum velocity V_(max) since the velocitycommand shape V**(t)<=V_(max).

$\begin{matrix}\begin{matrix}{{V^{*}(t)} = {\frac{D}{\int_{0}^{4\; t\; 0}{{V^{**}(t)}\ {t}}} \times}} \\{{V^{**}(t)} = {\frac{D}{{\int_{0}^{2t\; 0}{{{\overset{\sim}{V}}_{1}^{*}(t)}\ {t}}} + {\int_{0}^{2t\; 0}{{{\overset{\sim}{V}}_{2}^{*}(t)}\ {t}}}} \times}} \\{{V^{**}(t)} = {\frac{D}{D - E} \times {V^{**}(t)}}}\end{matrix} & (68)\end{matrix}$

As mentioned above, when generating a position command for moving themachine 4 to a target position under the constraint that a velocitycommand which is the first derivative with respect to time of theposition command cannot have a maximum which is equal to or larger thanthe velocity limit V_(max), the command generating device in accordancewith this embodiment 8 calculates a first velocity transition commandV₁*(t) tilde which changes the velocity of the machine 4 from zero tothe certain velocity limit V_(max) and a second velocity transitioncommand V₂*(t) tilde which changes the velocity of the machine 4 fromthe certain velocity limit to zero by using the velocity transitioncommand calculating unit 8, forms the velocity command which is thefirst derivative with respect to time of the position command from acombination of a product of the first velocity transition command V₁*(t)tilde and a constant number equal to or smaller than 1, a product of thesecond velocity transition command V₂*(t) tilde and a constant numberequal to or smaller than 1, and a fixed velocity equal to or smallerthan the velocity limit V_(max) by using the associating processing unit6, and carries out a process of associating an amount of travel providedby the position command with the target position without exciting anyvibration in the machine. Therefore, the command generating device inaccordance with this embodiment can obtain a position command whichprovides a velocity command which is the first derivative with respectto time of the position command and which does not have a maximumexceeding the velocity limit and prevents vibrations from occurring inthe machine. Using the velocity command which is the first derivativewith respect to time of the position command, the positioning operationcan be performed without any delay to the position command. Even wheneither the actuator or the machine has a velocity limit which theactuator or the machine shall not exceed in velocity, the commandgenerating device in accordance with this embodiment can form a positioncommand which properly positions the machine.

Embodiment 9

Each of a target machine to be driven and an actuator can have a maximumacceleration limit, as well as a maximum velocity limit which each ofthem shall not exceed in velocity. In such a case, the commandgenerating device according to either of above-mentioned embodimentsneeds to take an acceleration limit and a velocity limit of each of themachine and actuator into consideration, and, moreover, needs togenerate a position command which does not excite any vibration in themachine. In this embodiment 9, a method of forming a position commandX*(t) which does not excite any vibration in the machine inconsideration of a maximum acceleration and a maximum velocity will beexplained.

FIG. 31 is a block diagram showing the structure of an actuating controlsystem for actuating and controlling the machine, to which a commandgenerating device in accordance with embodiment 9 of the presentinvention is applied. The command generating device 1 calculates theposition command X*(t) based on an acceleration transition completiontime T, a target position D, a velocity limit V_(max), an accelerationlimit A_(max), and the vibration frequency ω and vibration dampingcoefficient ζ of the machine, using an acceleration transition commandcalculating unit 9 and an associating processing unit 6.

FIGS. 32 to 37 are a flowchart showing a process of obtaining theposition command X*(t) which is carried out by the command generatingdevice in accordance with embodiment 9. In step ST501 of FIG. 32, theacceleration transition completion time T, target position D, velocitylimit V_(max), acceleration limit A_(max), and vibration frequency ω andvibration damping coefficient ζ of the machine are provided to thecommand generating device 1.

In step ST502, the acceleration transition command calculating unit 9calculates an acceleration transition command a*(t) for changing theacceleration of the machine from zero to the acceleration limit A_(max)during the time period from the time t=0 to the time t=T withoutexciting any vibration in the machine, based on the vibration frequencyω and vibration damping coefficient ζ of the machine 4. This calculationis implemented using the method explained in, for example,above-mentioned embodiment 7.

The associating processing unit 6 carries out the following processing.In step ST503, the associating processing unit 6 calculates a firstacceleration command defined by the following equation (69) based on thefirst acceleration transition command a*(t).

$\begin{matrix}{{{\overset{\sim}{A}}_{1}^{*}(t)} = \left\{ \begin{matrix}{\alpha^{*}(t)} & \left( {0 \leqq t < T} \right) \\{A_{\max} - {\alpha^{*}\left( {t - T} \right)}} & \left( {T \leqq t < {2T}} \right) \\{- {\overset{\sim}{\alpha}\left( {t - {2\; T}} \right)}} & \left( {{2\; T} \leqq t < {3T}} \right) \\{{- A_{\max}} + {\alpha^{*}\left( {t - {3T}} \right)}} & \left( {{3T} \leqq t \leqq {4T}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (69)\end{matrix}$

In this equation, (A_(max)−a*(t−T)) indicates a second accelerationtransition command which changes the acceleration of the machine fromthe acceleration limit A_(max) to zero without exciting any vibration inthe machine, and (−A_(max)+a*(t−T)) indicates the second accelerationtransition command which changes the acceleration of the machine from anacceleration of −A_(max) to zero without exciting any vibration in themachine. Although the second acceleration transition command whichchanges the acceleration of the machine from the acceleration limitA_(max) to zero is calculated using the first acceleration commanda*(t), the second acceleration transition command which changes theacceleration of the machine from the acceleration limit A_(max) to zerocan be calculated using an acceleration transition command havinganother shape instead of the first acceleration command a*(t).

The associating processing unit 6 calculates a first velocity commandV₁(t) tilde (tilde phonetically means {tilde over ( )}) by integratingthe first acceleration command once with respect to time, and calculatesa first position command X₁(t) tilde (tilde phonetically means {tildeover ( )}) by integrating the first velocity command once with respectto time. The first velocity command is a velocity command having a valueother than zero during a time period 0<=t<=4T, and the first positioncommand becomes a position command for moving the machine from aninitial position to a certain position during the time period from thetime t=0 to the time t=4T.

In step ST504, the associating processing unit 6 calculates an amount oftravel provided by the first position command, i.e., an amount of traveld₁ according to the following equation (70). In step ST505, theassociating processing unit 6 compares the amount of travel d₁ providedby the first position command with the target position D, and, whendetermining that the amount of travel d₁ provided by the first positioncommand is not smaller than the target position D, the associatingprocessing unit 6 shifts to a command generation processing A of stepST506.

d ₁ ={tilde over (X)} ₁*(4T)  (70)

FIG. 33 is a flowchart explaining the command generation processing A.In step ST550, the associating processing unit 6 calculates a secondacceleration command A₂*(t) tilde (tilde phonetically means {tilde over( )}) by multiplying the first acceleration command by D/d₁, i.e., byusing the following equation (71):

Ã ₂*(t)=(D/d ₁)Ã ₁*(t)  (71)

The associating processing unit 6 calculates a second velocity commandby integrating the second acceleration command once with respect totime, and calculates a second position command by integrating the secondacceleration command twice with respect to time. These calculations area process of lowering the acceleration by multiplying the firstacceleration command by the constant D/d₁ equal to or less than 1, andof associating the second position command at a positioning time withthe target position. The second acceleration command which is obtainedby multiplying the first acceleration command by the constant D/d₁ isalso an acceleration command which does not excite any vibration in themachine. Furthermore, since the constant is equal to or smaller than 1,the second acceleration command indicates an acceleration equal to orsmaller than the acceleration limit. In step ST551, the associatingprocessing unit 6 calculates a maximum velocity of the second velocitycommand according to the following equation (72):

V ₂ ={tilde over (V)} ₂(2T)  (72)

In step ST552, the associating processing unit 6 compares the maximumvelocity V₂ of the second velocity command with the velocity limitV_(max). When, in step ST552, determining that the maximum velocity ofthe second velocity command does not exceed the velocity limit V_(max),the associating processing unit 6, in step ST553, determines that thesecond position command is the position command which is to bedetermined. The associating processing unit 6 multiplies the firstacceleration command by D/d₁ so as to associate the second accelerationcommand at the positioning time with the target position D, so thatX*(4T) becomes equal to D.

When, in step ST552, determining that the maximum velocity of the secondvelocity command exceeds the velocity limit V_(max), the associatingprocessing unit 6, in step ST554, calculates a time T₁=D/V_(max)−D/V₂.The associating processing unit 6 then, in step ST555, calculates anacceleration command according to the following equation (73):

$\begin{matrix}{{A^{*}(t)} = \left\{ \begin{matrix}{\left( {V_{\max}/V_{2}} \right){{\overset{\sim}{A}}_{2}^{*}(t)}} & \left( {0 \leqq t \leqq {2\; T}} \right) \\0 & \left( {{2T} \leqq t \leqq {{2T} + T_{1}}} \right) \\{\left( {V_{\max}/V_{2}} \right){{\overset{\sim}{A}}_{2}^{*}\left( {t - T_{1}} \right)}} & \left( {{{2T} + T_{1}} \leqq t \leqq {{4T} + T_{1}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (73)\end{matrix}$

In steps ST554 and ST555, the associating processing unit 6 performs aprocess of making the second acceleration command satisfy therequirement to limit the velocity of the machine to the velocity limitor less, and associating the position command at the positioning timewith the target position D. That is, since the velocity of the machineexceeds the velocity limit V_(max) if the drive control system carriesout the operation of positioning the machine using the secondacceleration command, the associating processing unit 6 multiplies thesecond acceleration command by V_(max)/V₂ so as to generate anacceleration command which accelerates the machine up to at most thevelocity V_(max).

However, since the amount of travel provided by this accelerationcommand is equal to DxV_(max)/V₂ even if this acceleration command isintegrated twice with respect to time, the associating processing unit 6performs a process of inserting only a time period of T₁ in which theacceleration is kept at zero between the acceleration time period(0<=t<=2T) and the deceleration time period (0<=t<=4T) of the secondacceleration command, and setting the velocity command during the timeperiod of T₁ to V_(max). The acceleration command which is thusdetermined in consideration of both the satisfaction of the requirementto limit the velocity of the machine to the velocity limit or less andthe association of the position command at the positioning time with thetarget position D is expressed by the above-mentioned equation (73). Theassociating processing unit 6, in step ST556, integrates theacceleration command A*(t) expressed by the above-mentioned equation(73) twice with respect to time so as to calculate the position commandX*(t) to be determined. When the associating processing unit 6 shifts tostep ST556, (V_(max)/V₂) is a constant equal to or less than 1 sinceV_(max)<=V₂ in step ST552.

When the target position D is larger than the amount of travel d₁provided by the first position command, in step ST505, the associatingprocessing unit 6, in step ST507, calculates a maximum velocity V₁ ofthe first velocity command according to the following equation (74):

V ₁ ={tilde over (V)} ₁*(2T)  (74)

The associating processing unit 6 then, in step ST508, compares themaximum velocity V₁ of the first velocity command with the velocitylimit V_(max). When determining that V₁ is smaller than V_(max), theassociating processing unit 6 shifts to a command generation processingB of step ST509, whereas when determining that V₁ is equal to or largerthan V_(max), the associating processing unit 6 shifts to a commandgeneration processing C of step ST510.

FIG. 34 is a flowchart for explaining the command generation processingB which is carried out when V₁ is smaller than V_(max) in step ST505.The associating processing unit 6, in step ST560, calculates a timeT₂=(V_(max)−V₁)/A_(max).

The associating processing unit 6, in step ST561, calculates the secondacceleration command according to the following equation (75). Theassociating processing unit 6 then, in step ST562, calculates a secondvelocity command V₂*(t) tilde (tilde phonetically means {tilde over ()}) by integrating the second acceleration command once with respect totime, and calculates a second position command X₂*(t) tilde (tildephonetically means {tilde over ( )}) by integrating the secondacceleration command twice with respect to time. The associatingprocessing unit 6 also, in step ST562, calculates a time T₃=2T+T₂.

$\begin{matrix}{{{\overset{\sim}{A}}_{2}^{*}(t)} = \left\{ \begin{matrix}{\alpha^{*}(t)} & \left( {0 \leqq t < T} \right) \\A_{\max} & \left( {T \leqq t < {T + T_{2}}} \right) \\{A_{\max} - {\alpha^{*}\left( {t - T - T_{2\;}} \right)}} & \left( {{T + T_{2}} \leqq t < {{2T} + T_{2}}} \right) \\{- {\alpha^{*}\left( {t - {2T} - T_{2}} \right)}} & \left( {{{2T} + T_{2}} \leqq T < {{3T} + T_{2}}} \right) \\{- A_{\max}} & \left( {{{3T} + T_{2}} \leqq T < {{3T} + {2T_{2}}}} \right) \\{{- A_{\max}} + {\alpha^{*}\left( {t - {3T} - {2T_{2}}} \right)}} & \left( {{{3T} + {2T_{2}}} \leqq T \leqq {{4T} + {2T_{2}}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (75)\end{matrix}$

Since the maximum velocity of the first velocity command does not exceedV_(max) in steps ST560 to ST563, the associating processing unit 6generates a command for making the maximum velocity reach V_(max). Thatis, since the first acceleration command is the one which changes theacceleration of the machine from zero to A_(max) during the time periodfrom the time t=0 to the time t=T, and then changes the acceleration ofthe machine from A_(max) to zero during the time period from the timet=T to the time t=2T, only a time period of T₂ during which theacceleration of the machine is kept at A_(max) (referred to as a uniformacceleration time period from here on) is inserted between the firsttime period 0<=t<=T and the second time period T<=t<=2T of the firstacceleration command in order to make the maximum velocity which themachine has according to the first acceleration command to reachV_(max). The second acceleration command thus determined is expressed bythe above-mentioned equation (75).

FIG. 35 is a flowchart for explaining the command generation processingC which is carried out when V₁ is larger than V_(max) in step ST505. Theassociating processing unit 6, in step ST570, calculates the secondacceleration command according to the following equation (76). In thiscase, since V₁ is larger than V_(max), (V_(max)/V₁) is a constant equalto or smaller than 1.

Ã ₂*(t)=(V _(max) /V ₁)×Ã ₁*(t)  (76)

The associating processing unit 6, in step ST571, calculates a secondvelocity command V₂*(t) tilde by integrating the second accelerationcommand once with respect to time, and also calculates a second positioncommand X₂*(t) tilde by integrating the second acceleration commandtwice with respect to time. The associating processing unit 6 then, instep ST572, calculates a time T₃₌₂T. Since the maximum velocity of thefirst velocity command exceeds V_(max) in steps ST570 to ST572, theassociating processing unit 6, performs a process of multiplying thefirst acceleration command by V_(max)/V₁ so as to make the maximumvelocity of the second velocity command be equal to V_(max). Theassociating processing unit 6, in step ST511, calculates an amount oftravel d₂ provided by the second position command and calculated byeither the command generation processing B of step ST509 or the commandgeneration processing C of step ST510 according to the followingequation (77):

d ₂ ={tilde over (X)} ₂*(2T ₃)  (77)

The associating processing unit 6, in step ST512, compares the targetposition D with the amount of travel d₂ provided by the second positioncommand, and, when determining that D is equal to or larger than d₂,shifts to a command generation processing D of step ST513, whereas whendetermining that D is smaller than d₂, shifts to a command generationprocessing E of step ST514.

FIG. 36 is a flowchart for explaining the command generation processingD which is carried out when D is equal to or larger than d₂ in stepST512. The associating processing unit 6, in step ST580, calculates atime T₄=(D−d₂)/V_(max). The associating processing unit 6 then, in stepST581, calculates a velocity command V*(t) according to the followingequation (78). The associating processing unit 6, in step ST582,calculates the position command X*(t) which is to be determined byintegrating the velocity command V*(t) once with respect to time.

$\begin{matrix}{{V^{*}(t)} = \left\{ \begin{matrix}{{\overset{\sim}{V}}_{2}^{*}(t)} & \left( {0 \leqq t < T_{3}} \right) \\V_{\max} & \left( {T_{3} \leqq t < {T_{3} + T_{4}}} \right) \\{V_{\max} - {{\overset{\sim}{V}}_{2}\left( {t - T_{3} - T_{4}} \right)}} & \left( {{T_{3} + T_{4}} \leqq t \leqq {{2\; T_{3}} + T_{4}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (78)\end{matrix}$

In steps ST580 to ST582, since the amount of travel provided by thesecond position command X₂(t) tilde does not reach the target positionD, the associating processing unit 6 performs a process of compensatingfor the amount of travel which is short. That is, only a time period ofT₄ which the velocity of the machine is kept at V_(max) is insertedbetween the acceleration time period (0<=T<=T₃) and the decelerationtime period (T₃<=T<=2T₃) of the second velocity command. This processingcorresponds to the above-mentioned equation (78).

FIG. 37 is a flowchart for explaining the command generation processingE which is carried out when D is smaller than d₂ in step ST513. Theassociating processing unit 6, in step ST590, calculates V3 from thefirst velocity command according to the following equation (79). Theassociating processing unit 6 then, in step ST591, solves the followingequation (80) which is a quadratic equation with respect to ζ, and setsa solution having a larger value to T₅.

V ₃ ={tilde over (V)} ₁*(T)  (79)

A _(max)ξ+2(V ₃ +A _(max) T)ξ−(D−d ₁)=0  (80)

The associating processing unit 6, in step ST592, calculates theacceleration command A*(t) according to the following equation (81). Theassociating processing unit 6 then, in step ST593, obtains the positioncommand X*(t) by integrating the acceleration command A*(t) twice withrespect to time.

$\begin{matrix}{{A^{*}(t)} = \left\{ \begin{matrix}{\alpha^{*}(t)} & \left( {0 \leqq t < T} \right) \\A_{\max} & \left( {T \leqq t < {T + T_{5}}} \right) \\{A_{\max} - {\alpha^{*}\left( {t - T - T_{5\;}} \right)}} & \left( {{T + T_{5}} \leqq t < {{2T} + T_{5}}} \right) \\{- {\alpha^{*}\left( {t - {2T} - T_{5}} \right)}} & \left( {{{2T} + T_{5}} \leqq T < {{3T} + T_{5}}} \right) \\{- A_{\max}} & \left( {{{3T} + T_{5}} \leqq T < {{3T} + {2T_{5}}}} \right) \\{A_{\max} + {\alpha^{*}\left( {t - {3T} - {2T_{5}}} \right)}} & \left( {{{3T} + {2T_{5}}} \leqq T \leqq {{4T} + {2T_{5}}}} \right) \\0 & ({otherwise})\end{matrix} \right.} & (81)\end{matrix}$

Since the amount of travel provided by the second position command X₂(t)tilde exceeds the target position D in steps ST590 to ST593, theassociating processing unit 6 performs the process of associating theposition command at the positioning time with the target position D byreducing the uniform acceleration time period of the second accelerationcommand (Since the associating processing unit multiplies the firstacceleration command by the constant smaller than 1 so as to obtain thesecond acceleration command when shifting to the command generationprocessing C in step ST509, the amount of travel d₂ provided by thesecond position command is smaller than the amount of travel d₁ providedby the first position command. That is, the associating processing unitcalculates a uniform acceleration time period of T₅ in order toassociate the position command at the positioning time with the distanceD according to the above-mentioned equation (80), and inserts only theuniform acceleration time period of T₅ during which the acceleration ofthe machine is kept at A_(max) between the first time period 0 <=t<=Tand the second time period T<=t<=2T of the first acceleration commandaccording to the above-mentioned equation (81). For this reason, whenshifting to the command generation processing C of step ST508, theassociating processing unit does not shift to the command generationprocessing D of step ST513 in step ST512). This is the accelerationcommand A*(t) given by the above-mentioned equation (81).

The position command X*(t) is thus obtained according to theabove-mentioned flow, and the position command is calculated by eitherof the command generation processings A, D, and E. The accelerationcommand which is the second derivative with respect to time of theposition command is provided by the above-mentioned equation (71) whenthe associating processing unit shifts to the command generationprocessing A of step ST553, is provided by the above-mentioned equation(73) when the associating processing unit shifts to step ST555 of thecommand generation processing A, is provided by the above-mentionedequation (75) or (76) when the associating processing unit shifts to thecommand generation processing D, and is provided by the above-mentionedequation (81) when the associating processing unit shifts to the commandgeneration processing E.

Noting that the first acceleration command A₁*(t) tilde consists of thefirst acceleration transition command that changes the acceleration ofthe machine from zero to the acceleration limit A_(max) without excitingany vibration in the machine, and the second acceleration transitioncommand that changes the acceleration of the machine from theacceleration limit A_(max) to zero without exciting any vibration in themachine, as shown in the above-mentioned equation (69), the accelerationcommand given by the above-mentioned equations (71), (73), (75), (76),and (81) consists of the first acceleration transition command thatchanges the acceleration of the machine from zero to the accelerationlimit A_(max) without exciting any vibration in the machine, the secondacceleration transition command that changes the acceleration of themachine from the acceleration limit A_(max) to zero without exciting anyvibration in the machine, a product of the second accelerationtransition command and a constant equal to or smaller than 1, 0, and themaximum acceleration A_(max).

Therefore, the positioning control can be carried out properly so thatthe acceleration of the machine which is provided by the positioncommand which is obtained by integrating the acceleration commands twicewith respect to time does not exceed the acceleration limit. Inaddition, the associating processing is carried out so that the positioncommand at the positioning time can be associated with the targetposition D, and the velocity command which is the first derivative withrespect to time of the position command can have a value equal to orsmaller than the velocity limit. The position command obtained accordingto the above-mentioned flow satisfies the conditions of the accelerationlimit and velocity limit, and causes the machine to reach the targetposition D without exciting any vibration in the machine.

Next, advantages offered by the present embodiment will be explainedwith reference to numerical calculation examples. Assume that thecommand generating device generates a position command for a case wherethe vibration frequency of the machine 4 is 10 Hz (ω=2nπ·10=31.4[rad/s]), the vibration damping coefficient of the machine is ζ=0.03,the target position is D=0.2, the velocity limit V_(max) is 0.5, and theacceleration limit is 2.0. First, the description will be directed to anumerical calculation example to which the position command inaccordance with the present embodiment is not applied, but to which atrapezoid-shaped velocity command which makes the most of the velocitylimit and acceleration limit and which is the first derivative withrespect to time of the position command is applied.

FIGS. 38A to 38D are graphs showing the numerical calculation example towhich the position command in accordance with the present embodiment 9is not applied, but to which a trapezoid-shaped velocity command isapplied. FIG. 38A is a graph showing the position command and themachine's position, FIG. 38B is an enlarged view of FIG. 38A, FIG. 38Cis a graph showing the velocity command and the machine's velocity, andFIG. 38D is a graph showing the acceleration command and the machine'sacceleration. Solid lines shown in FIGS. 38A and 38B indicate themachine's position, and dotted lines indicate the position command. Asolid line shown in FIG. 38C indicates the machine's velocity, and adotted line indicates the velocity command which is the first derivativewith respect to time of the position command. A solid line in FIG. 38Dindicates the machine's acceleration, and a dotted line indicates theacceleration command which is the second derivative with respect to timeof the position command.

It is apparent from the velocity command of FIG. 38C and accelerationcommand of FIG. 38D that these commands maximize the utilization of theacceleration limit and velocity limit. In addition, it is apparent fromthe machine's position of FIG. 38B, machine's velocity of FIG. 38C, andmachine's acceleration of FIG. 38D that a residual vibration occurs inthe machine and the settling characteristics at the time of positioningcontrol get worse. It is further apparent from the machine's velocity ofFIG. 38C and machine's acceleration of FIG. 38D that the residualvibration caused by the trapezoid-shaped velocity command results in themachine's velocity exceeding the velocity limit and the machine'sacceleration exceeding the acceleration limit.

Next, a numerical calculation example to which the position command inaccordance with this embodiment is applied will be explained. Assumethat the acceleration transition completion time T is 0.09 seconds.FIGS. 39A to 39D are graphs showing the numerical calculation example towhich the position command in accordance with this embodiment isapplied. FIG. 39A is a graph showing the position command and themachine's position, FIG. 39B is an enlarged view of FIG. 39A, FIG. 39Cis a graph showing the velocity command and the machine's velocity, andFIG. 39D is a graph showing the acceleration command and the machine'sacceleration. Solid lines shown in FIGS. 39A and 39B indicate themachine's position, and dotted lines indicate the position command. Asolid line shown in FIG. 39C indicates the machine's velocity, and adotted line indicates the velocity command which is the first derivativewith respect to time of the position command. A solid line in FIG. 39Dindicates the machine's acceleration, and a dotted line indicates theacceleration command which is the second derivative with respect to timeof the position command.

It is apparent from the velocity command of FIG. 39C and accelerationcommand of FIG. 39D that these commands maximize the utilization of theacceleration limit and velocity limit. In addition, it is apparent fromthe machine's position of FIG. 39B, machine's velocity of FIG. 39C, andmachine's acceleration of FIG. 39D that no residual vibration occurs inthe machine and the settling characteristics at the time of positioningcontrol are good. It is further apparent from the machine's velocity ofFIG. 39C and machine's acceleration of FIG. 39D that the machine'svelocity does not exceed the velocity limit and the machine'sacceleration does not exceed the acceleration limit.

This embodiment thus offers an advantage of being able to obtain theposition command into which information about an acceleration and avelocity which the actuator or the machine can generate is incorporatedwithout exciting any vibration in the machine during the positioningcontrol. This embodiment offers another advantage of being able toreduce the time required for the positioning control because theutilization of the acceleration limit and velocity limit is maximized.

As shown in FIGS. 39A to 39D, the acceleration command during theacceleration time period or the deceleration time period is continuous,and does not experience any rapid change which rises during theacceleration time period (or during the deceleration time period), afterthat, descends in a short time, and then rises again. In this case, manyhigh-frequency components are not contained in the acceleration commandsignal. The command generating device in accordance with the presentembodiment thus offers a further advantage of making it difficult forvibrations resulting from high-frequency components contained in thecommand to be excited in the machine.

Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

1. A command generating device comprising: a storage means forestablishing an equation indicating a frequency component of an nthderivative command shape signal having a value which is equal to a fixedmultiple of an nth derivative with respect to time of a position commandfor causing a target to be driven and controlled to reach a targetposition at a positioning time, and which is specified by a certainparameter, the frequency component depending upon said parameter, forpredetermining frequencies at which said equation indicating thefrequency component becomes equal to zero dependent upon said parameter,and for storing both said parameter and said frequencies at which theequation indicating the frequency component of said nth derivativescommand shape signal becomes equal to zero by associating them with eachother; a command shape calculating means for reading said parametercorresponding to a frequency of a vibration which occurs in said targetto be driven and controlled, at which said equation indicating thefrequency component becomes equal to zero, from said storage means so asto determines said nth derivative command shape signal using saidparameter; and an associating processing means for integrating said nthderivative command shape signal which is calculated from said positioncommand by said command shape calculating means n times with respect totime, and for multiplying the integral result by a constant whichassociates the position command at said positioning time with saidtarget position so as to determine the position command.
 2. The commandgenerating device according to claim 1, wherein when the positioningtime is 2 t ₀, said storage means defines an acceleration command shapesignal, which has a value equal to a fixed multiple of a secondderivative with respect to time of the position command and which isspecified by the certain parameter r, as sin(nt/(2 rt ₀)) for a timeperiod from a time t=0 to a time t=rt₀, as 1 for a time period from atime t=rto to a time t=(1−r)t₀, as cos [π{t−(1−r)t₀}/(2 rt ₀)] for atime period from a time t=(1−r)t₀ a time t=t₀, as −sin [n(t−t₀)/(2 rt₀)] for a time period from a time t=t₀ a time t=(1+r)t₀, as −1 for atime period from a time t=(1+r) to to a time t=(2−r)t₀, as cos[n{t−(2−r)t₀}/(2 rt ₀)] for a time period from a time t=(2−r)t₀ a timet=2 t ₀, and as 0 for other time periods, and establishes an equationindicating a frequency component of said acceleration command shapesignal depending upon said parameter r and stores frequencies at whichsaid equation indicating the frequency component of said accelerationcommand shape signal becomes equal to zero dependent upon said parameterand said positioning time while associating the frequencies and saidpositioning time with each other.
 3. The command value generating deviceaccording to claim 1, wherein, when the positioning time is 2 t ₀, saidstorage means defines an acceleration command shape signal A**(t), whichhas a value equal to a fixed multiple of a second derivative withrespect to time of the position command and which is specified by thecertain parameter r, as −cos(πrt/2 t ₀) for a time period from a timet=0 to a time t=t₀, as −cos(πr(2 t ₀−t)/2 t ₀) for a time period from atime t=t₀ a time t=2 t ₀, and as 0 for other time periods, andestablishes an equation indicating a frequency component of saidacceleration command shape signal depending upon said parameter r, andpredetermines frequencies at which said equation indicating thefrequency component of said acceleration command shape signal becomesequal to zero dependent upon said parameter r, and stores said parameterand both the frequencies at which said equation indicating the frequencycomponent of said acceleration command shape signal becomes equal tozero and said positioning time while associating them with each other.4. The command generating device according to claim 1, wherein saidcommand shape calculating means calculates the nth derivative commandshape signal having a value which is equal to a fixed multiple of thenth derivative command of said position command so that a convolution ofan impulse response of a transfer function which is determined from afrequency a) of a vibration which occurs in said target to be driven andcontrolled, and the nth derivative with respect to time of the positioncommand becomes equal to zero, the convolution being calculated over atime period from the positioning time onward, integrates the nthderivative command shape signal which is obtained from the positioncommand (n−1) times with respect to time so as to determine a firstvelocity command shape signal, and multiplies said first velocitycommand shape signal by a positive constant g and a function withrespect to time t which is determined from exp (−gt) so as to determinea velocity command shape signal having a value which is equal to a fixedmultiple of the first derivative with respect to time of the positioncommand.
 5. The command generating device according to claim 4, whereinsaid command shape calculating means determines the constant g using thevibration frequency ω and a vibration damping coefficient ζ according toζ/(1−ζ²)^(1/2)ω.
 6. The command generating device according to claim 1,wherein when sequentially positioning the target to be driven andcontrolled to two or more target positions at two or more correspondingpositioning times, respectively, said command generating devicecalculates two or more position commands for causing said target to bedriven and controlled to reach said two or more target positions at saidtwo or more corresponding positioning times, respectively.